Wireless Networks Have Benefits Beyond Saving Money on Cabling Costs

p10 With Great Power Comes Network Data p16 Obstacles and Mysteries of a Wireless Implementation p26 Diagnostics: Use What You Have

Q3 • 2009

Q2 • 2009

Q2 • 2009

More ThanLess Wire

IN09Q3_01_Cover2.indd 8 7/15/09 2:10 PM

Our STRIDE family of industrial grade unmanaged Ethernet switches and media converter is specifically built for industrial environments.Install Stride switches and your Ethernet control network will maintain more consistent cycle times even under heavy I/O and dataexchange. The new aluminum-housed models offer a wider operating temperature range (-40 to +85 deg. C).

Product Description STRIDE PLASTIC MODELSPrice/Part Number

CHECK OUT PRICES ON ETHERNET SWITCHES

AutomationDirect prices are U.S. published prices as of April 2009. Prices subject to change without notice.

5-port Ethernet switch with five 10/100BaseTRJ45 Ethernet ports

8-port Ethernet switch with eight 10/100BaseTRJ45 Ethernet ports

Ethernet-Fiber converter with one 10/100BaseT RJ45Ethernet port and one 100BaseFX fiber optic port

5-port Ethernet switch with four 10/100BaseT RJ45Ethernet ports and one 100BaseFX fiber optic port

$ 99.00SE-SW5U

9-port Ethernet switch with eight 10/100BaseT RJ45Ethernet ports and one 100BaseFX fiber optic port

AutomationDirectSTRIDE METAL MODELSPrice/Part Number$ 199.00

SE-SW5U-WT

$ 172.00SE-SW8U

$ 259.00SE-SW8U-WT

$ 172.00SE-SW5U-ST

$ 259.00SE-SW5U-ST-WT

$ 242.00SE-SW9U-ST

$ 339.00SE-SW9U-ST-WT

$ 162.00SE-MC2U-ST

Advanced Industrial Hardware• All 10/100BaseT RJ45 ports are auto-detecting,

auto-crossover and auto-polarity• Redundant power inputs with surge and spike protection• Optional 100Mbps multimode fiber optic port for

distances up to 4km• UL, CSA (CUL), and CE certified; rated for Class 1, Div. 2

Real-time Performace• Store and forward wire speed switching - no delays• Full-duplex operation with flow control (no collisions!)• Auto crossover (MDI/MDIX) and auto polarity

True Industrial Design• Ethernet Isolation -1500 VRMS 1 minute• Spike protection - 5,000 watts (10x for 10 uS)• UL (CUL) listed and CE certified• Hazardous locations rated for Class 1, Div. 2

For complete information or to order our free catalog, visit: www.automationdirect.com/ethernet

1-800-633-0405

www.automationdirect.com

0908-IndustrialNetworking-Comm-MAG:comm 7/2/2009 3:58 PM Page 1

IN09Q3_FPA.indd 2 7/15/09 11:07 AM

Our STRIDE family of industrial grade unmanaged Ethernet switches and media converter is specifically built for industrial environments.Install Stride switches and your Ethernet control network will maintain more consistent cycle times even under heavy I/O and dataexchange. The new aluminum-housed models offer a wider operating temperature range (-40 to +85 deg. C).

Product Description STRIDE PLASTIC MODELSPrice/Part Number

CHECK OUT PRICES ON ETHERNET SWITCHES

AutomationDirect prices are U.S. published prices as of April 2009. Prices subject to change without notice.

5-port Ethernet switch with five 10/100BaseTRJ45 Ethernet ports

8-port Ethernet switch with eight 10/100BaseTRJ45 Ethernet ports

Ethernet-Fiber converter with one 10/100BaseT RJ45Ethernet port and one 100BaseFX fiber optic port

5-port Ethernet switch with four 10/100BaseT RJ45Ethernet ports and one 100BaseFX fiber optic port

$ 99.00SE-SW5U

9-port Ethernet switch with eight 10/100BaseT RJ45Ethernet ports and one 100BaseFX fiber optic port

AutomationDirectSTRIDE METAL MODELSPrice/Part Number$ 199.00

SE-SW5U-WT

$ 172.00SE-SW8U

$ 259.00SE-SW8U-WT

$ 172.00SE-SW5U-ST

$ 259.00SE-SW5U-ST-WT

$ 242.00SE-SW9U-ST

$ 339.00SE-SW9U-ST-WT

$ 162.00SE-MC2U-ST

Advanced Industrial Hardware• All 10/100BaseT RJ45 ports are auto-detecting,

auto-crossover and auto-polarity• Redundant power inputs with surge and spike protection• Optional 100Mbps multimode fiber optic port for

distances up to 4km• UL, CSA (CUL), and CE certified; rated for Class 1, Div. 2

Real-time Performace• Store and forward wire speed switching - no delays• Full-duplex operation with flow control (no collisions!)• Auto crossover (MDI/MDIX) and auto polarity

True Industrial Design• Ethernet Isolation -1500 VRMS 1 minute• Spike protection - 5,000 watts (10x for 10 uS)• UL (CUL) listed and CE certified• Hazardous locations rated for Class 1, Div. 2

For complete information or to order our free catalog, visit: www.automationdirect.com/ethernet

1-800-633-0405

www.automationdirect.com

0908-IndustrialNetworking-Comm-MAG:comm 7/2/2009 3:58 PM Page 1

Before there was OMEGAMATIONTM there was Rube GoldbergVisit—

omegamation.comTM

To order your FREEPremier Editionomegamation.comTM

Complete AutomationHandbook and Encyclopedia.It’s loaded with thousandsof Automation products and over 200 pages of technical reference!

Where Do I Go for Automation Products?omegamation.com, of Course!

omega.com/809IN3

Direct Link:

© COPYRIGHT 2009 OMEGA ENGINEERING, INC. ALL RIGHTS RESERVED

omegamation.comsm

Shop Online at

Cover Art: Based on an original Norman Rockwell Illustration © The Curtis Publishing Company Rube Golberg © Rube Goldberg, Inc.

1-888-55-663421-888-55-OMEGA

TM

For Sales and Service, Call TOLL FREE

Your single source for process measurement and control products!

Starts at $134

NEED MORE

CARTOONS?

FREE!HARDBOUNDHANDBOOK

FREE!HARDBOUNDHANDBOOK

Go to: www.omegamation.com for your daily dose of RUBE GOLDBERG!

ELC Programmable Logic Controllers

and Modules

Visit omega.com/elcELC Series

Visit omega.com/DRF_075M

Remote Monitoring Built-In EthernetProtocol Converter Visit omega.com/G3_HMi306

Web-Enabled Graphic OperatorInterface Terminals G3 Series HMI

Starts at $599

Rotary Actuators—Pneumatic, FlangeMountable DRF DirectConnectTM Series

DRF Series

DLT-10M-E-C-50linear slide, $270

DMEX mounting stanchions,start at $18ODRF-004

turntable module to attach

grippers, $49DPP-10M-12 parallelgripper, $415 withOSTW-K-M thermocouple connector, $2.25

USA

MADEMADEININ

Universal Remote I/OModules, DIN RailMountable Modbus® I/OHE359 Series Starts at $200

Low-Cost Compact “All-in-One”Controllers

OCS XL Series

Visit omega.com/xl-ocsUSA

MADEMADEININ

Starts at $445

Visit omega.com/HE359

Starts at $351

IN09Q3_FPA.indd 3 7/20/09 9:23 AM

IN09Q3_FPA.indd 4 7/15/09 2:05 PM

7 FIRST BIT With Great Power ...

8 PACKETS Smart Objects Use Internet Protocol

10 BANDWIDTH Power to the Field Devices, Right On

24 PRODUCTS

26 PARITY CHECK Diagnostics—Use What You Have

COLUMNS & DEPARTMENTS

COVER STORY

INDUSTRIAL NETWORKING is published four times annually to select subscribers of CONTROL and CONTROL DESIGN magazines by PUTMAN MEDIA INC. (also publishers of CHEMICAL PROCESSING, FOOD PROCESSING, PHARMACEUTICAL MANUFACTURING and PLANT SERVICES), 555 W. Pierce Road, Suite 301, Itasca, IL. (Phone: 630/467-1300; Fax: 630/467-1124.) Address all correspondence to Editorial and Executive O� ces, same address. ©Putman Media 2009. All rights reserved. The contents of this publication may not be reproduced in whole or part without consent of the copyright owner. INDUSTRIAL NETWORKING assumes no responsibility for validity of claims in items reported. Single copies $15.

More Than Less WireWireless Networks Have Bene� ts Beyond Saving

Money on Cabling Costs

BY DAN HEBERT, PE,SENIOR TECHNICAL EDITOR

E V A L U A T E 1 2

For additional information, please contact Foster Printing Service, the official reprint provider for Industrial Networking.

PMS 370 C

C: 60M: 0Y: 100K: 28

Call 866.879.9144 or sales@fosterprinting.com

RepRints aRe ideal foR:

n New Product Announcements

n Sales Aid For Your Field Force

n PR Materials & Media Kits

n Direct Mail Enclosures

n Customer & Prospect Communications/Presentations

n Trade Shows/Promotional Events

n Conferences & Speaking Engagements

n Recruitment & Training Packages

Use reprints to maximize

your marketing initiatives and

strengthen your brand’s value.

Reprints are a simple way to put information directly into the hands of

your target audience. Having been featured in a well-respected publication

adds the credibility of a third-party endorsement to your message.

Custom REPRINts

16

INDUSTRIAL NETWORKING

Q3 • 20095

The Once and Future Network Tra� c CopsRouters and Switches Continue to Manage and Direct Data on the Network Information Highway

R E S E A R C H 2 0

Wireless: The Real WorldFrustrating Obstacles and Unexpected Mysteries of a Wireless Network Project Aren’t Covered in the Manual

BY ALICE MCWILLIAMS, CHEVRON PHILLIPS

I M P L E M E N T 1 6

IN09Q3_05_TOC.indd 5 7/16/09 9:39 AM

IN09Q3_FPA.indd 6 7/15/09 11:08 AM

7

Power over ethernet (Poe) is therelatively new ability to provide low power, along with data, to devices via standard ethernet cable.

Poe, however, is not so new that it already hasn’t been standardized by ieee. As explained in this issue’s Bandwidth column on Poe, ieee’s spec defines the powered device (PD) and the power sourcing equipment (Pse), a separate device typically installed in the wiring closet near

the ethernet switch or hub that inserts dc voltage onto the twisted pair cable and can be either an endpoint or a midspan device. An endpoint Pse contains both the data communication capabilities and the power-delivery mechanism, while a midspan only contains the power delivery mechanism and is inserted in the network between the non-Poe-capable ethernet switch and the PD.

this past spring, PhihongUsA (www.phihong.com) claimed to have developed a Poe midspan product line capable of offering 95 w of power per port. the Phihong midspan’s 95 w theoretically makes it suitable for high-power applications such as computer workstations, LCD panels and wireless-access-point arrays. Phihong says the new midspan provides ieee 802.3af detection and disconnect, as well as pre-standard ieee802.3at classification, and offers voltage, current and circuit protection.

Despite its claims of safety and pseudo-compliance, this is an example of a manufacturer reaching outside the realms of standardization and interoperability to push the envelope. But with great power comes great capability.

“As long as the ieee 802.3 standard is followed, there are no risks, neither from the safety nor from the data damage point of view,” says Daniel Feldman, Poe/Poe+ subcommittee technical chair of the ethernet Alliance (www.ethernetalliance.org) and director of marketing for Microsemi (www.microsemi.com). “Currently, ieee 802.3 supports supplying up to 12.95 w to the powered device on Cat. 3 and above cables. The ieee 802.3at task force is working to modify ieee 802.3 so it supports delivering 25.5 w on Cat. 5 and above cables, using two pairs of wires. The ieee 802.3at standard is being written so it’s feasible to deliver on a single Cat. 5 cable up to 51 w using four pairs of wires. it may or may not be safe, and data might

or might not be damaged when a higher amount of power is delivered on a cable.”

The first and most obvious risk of some Poe products touting the ability to offer power as high as 95 w per port is the current capacity of the 24 AwG conductors, which in this application is roughly 500 mA per conductor, explains eric Juillerat, president and Ceo of raven technology Group (www.raventechllc.com). “exceeding this

can present cable failure probabilities,” he says. “some speculate that the combination of the cable and the rJ45 allow higher current ratings. however, i am not aware of any tests confirming this officially. i believe that Poe technology in the future will be capable of higher power, but at this time it is not practical.”

The risk of high power would be an introduction of noise into the system via the Cat. 6 cable, explains Doug erlemann, business development manager-cameras for Baumer Group (www.baumergroup.com). “The 802.3 spec states that 13.5 w are required at the end of 100 m,” he says. “our cameras, for example, draw less than 5.5 w.”

The biggest risk is that the power will be used for driving i/o output channels directly, which would quickly exceed the current limitation of ieee 802.3af, exceed the current capabilities of the Cat. 5 data wires’ conductors and also introduce excessive noise to the data lines, explains Joey stubbs, Pe, PMP, north American representative, etherCat technology Group (www.ethercat.org). “Keep in mind that the original purpose of Poe was to power low-wattage electronics such as internet telephones, small microprocessors and LAn access points,” he says. And regardless, 95 w still is low power and incapable of driving i/o or pneumatic valves, notes stubbs.

organizations that opt for high-power Poe products are purchasing products that aren’t standards-based, warns Art Felgate, product manager, transition networks (www.transition.com). “The forthcoming ieee 802.3at Poe+ standard will only support at most 30 w,” he explains. “ratification of this standard should occur later this fall. in the long run, those companies could incur unexpected, higher costs if they move from the non-standard solutions to standards-compliant ones.”

With Great Power ...OrganizatiOns

that Opt fOr high-

pOwer pOe prOducts

are purchasing

prOducts that are

nOt standards-based.

f i r s t b i t

MIKE BACIDOREManaging editOr

mbacidore@putman.net

7industrial netwOrking

Q3 • 2009f i r s t b i t

IN09Q3_07_FirstBit.indd 7 7/17/09 1:42 PM

IndustrIal networkIng

Q3 • 20098 p a c k e t s

Smart Objects Use Internet Protocol

Interconnected smart objects, the everyday devIces around us wIth embedded sensors providing information to a host application, “represent a quantum leap in the way technology will be applied in the coming century,” notes Geoff mulligan, chairman of the IPso alliance (www.ipso-alliance.org), an organization promoting a network that will allow sensor-enabled physical objects to talk to one another via an Internet protocol for smart objects (IPso).

a so-called “smart object” is any device that combines processing power, communications capabilities and a power source to provide real-time information to a computer system. Integration of the Internet protocol, which allows the Internet to run smoothly, in turn allows smart objects to communicate directly with one another over the existing global network following a proven protocol that has been in place for nearly 35 years. The IP framework additionally provides scalability, a vital feature for large organizations.

one particularly notable aspect of this organization’s mission is that the technology exists today. The standards do not provide a future plan for what will be accomplished in the next year or decade, but rather what is here now. an organization wishing to deploy this technology can do so immediately and with confidence that the infrastructure of the network will be around in the foreseeable future.

new member organizations include such familiar names as Intel, bosch and johnson controls, along with more specialized tech and wireless firms cea, convergence wireless, ece, ember, Iar systems, Ibit world, InrIa, maxfor, national semiconductor, somfy, tridium and ZeroG wireless rounding out the latest group of companies to join the organization.

These new members bring IPso’s corporate membership to 51, joining companies such as cisco, ericsson, saP, sun microsystems and texas Instruments.

“Intel believes the IPso alliance will be an integral group to enable the interoperability and connectivity of devices for the embedded Internet,” says tony neal-Graves, general manager, strategic planning, embedded and communications group, Intel (www.intel.com). “Intel architecture has played a central role in the build-out of the Internet, and we’re committed to delivering products and technology that will enable billions of embedded, connected devices.”

a need exists for an open and informal association of like-minded organizations to promote the value of using the Internet protocol for the networking of smart objects, says harald hoenninger, vP corporate research at bosch (www.bosch.us). “standards for embedded IP will foster an open-systems approach and achieve high interoperability levels, which are crucial,” he says. “as members of the IPso alliance, we plan to take a role in the existing and evolving business ecosystems of embedded It.”

This connectivity between physical objects across so many facets represents a quantum leap in the way technology will be applied, says mulligan. “It also explains why so many essential technology companies are joining in our efforts,” he adds. “The numerous areas of life and platforms that will be impacted are reflected in the caliber of companies partnering with us in these early stages. we expect to see more well-known organizations joining with us in the months ahead.”

The introduction of IP sensors and smart objects marries It systems with hvac, energy, fire, security and lighting systems, notes joseph noworatzky, vice president of engineering for johnson controls (www.johnsoncontrols.com). “This convergence of systems creates new synergies and applications for our customers not feasible across independent networks,” he says.

Bits & Bytes

GE Global Research (www.ge.com/research) was awarded $2 million in federal stimulus funding from the U.S. Department of Defense for a smart microgrid demonstration project at Twentynine Palms Base, Calif., the world’s largest Marine Corps base.

Wurldtech Security Technologies (www.wurldtech.com), provider of the Achilles Platform and other cybersecurity testing and certification solutions, expanded the capabilities of the Achilles Network Testing Platform to include test suites for emerging industrial wireless protocols.

Rockwell Automation (www.rockwellautomation.com) and ProLeiT (www.proleit.com) reached a global agreement allowing ProLeiT to more tightly integrate its Plant iT with the Rockwell Automation Logix control platform.

HART Communication Foundation (www.hartcomm.org) released its Wireless Test System, an update to the HART Test System, a set of testing tools designed to ensure interoperability of HART-enabled devices.

Igus (www.igus.com) product experts are available to examine cable carriers and continuous-flex cables free of charge during plant shutdowns in August.

The 1 millionth Anybus communications module was produced by HMS Industrial Networks (www.anybus.com).

IPSO Alliance demonstrated interoperability by linking global sensors to a graphical application display at a recent trade show. More than 100,000 readings from sensors spread throughout Korea, Finland, Sweden, Switzerland, Canada, the U.K. and the U.S. were collected.

IPso

aLL

Ian

ce

IN09Q3_08_09_Packets.indd 8 7/16/09 9:47 AM

9IndustrIal networkIng

Q3 • 2009

FDI Effort Inches Toward SolutionThe Field device inTegraTion (Fdi) Project Team, a cooperative effort among process control suppliers and members of the electronic device description language (eddl) cooperation Team (ecT), has performed a complete inventory of use case analysis and designed a draft architecture concept and draft functional specifications in its effort to develop a common Fdi solution.

The architecture is a client/server structure based on oPc Unified architecture (oPc Ua) technologies. The field device integration is realized by a “device package” provided by the device supplier containing eddl components and an optional programmed component for programmed user interfaces. This is designed to allow complete flexibility to develop customized user interfaces.

The current phase of the project includes development of the detail specifications followed by validation of the specifications by each of the member organizations.

details of the exact Fdi architecture and associated device interface will be unveiled with the release of the final functional specification, currently planned for the summer of 2010.

Fieldbus Foundation, FdT group, harT communication Foundation, oPc Foundation and Profibus nutzer-organisation comprise the ecT.

Gas Detection to Reach $823 MillionThe worldwide markeT For Toxic and combustible gas detectors is expected to grow at a compounded annual growth rate (cagr) of nearly 4% over the next five years, according to an arc advisory group (www.arcweb.com) study. The market was $689 million in 2008 and is forecasted to be $823 million in 2013, the report says.

after brisk growth earlier in the decade, the market will take a brief respite as companies shift their emphasis from large

capital projects to upgrading their installed bases of equipment and keeping their operational expenses as low as possible, says allen avery, principal author of the study. “Though the down economy will have a dampening effect over the short term, the need for toxic gas detectors to

protect plant personnel and communities still remains,” he says. regionally, suppliers can expect to see the largest growth in the middle east, due to its high concentration of oil and gas activities, and in asia, where heavy investment in plant construction continues in core sectors.

251-342-2164 • N-TRON_Sales@n-tron.com • www.n-tron.com

708 Series Fully Managed Fast Ethernet

708FX2 Series Fully Managed Fast Ethernet

716 Series Fully Managed Fast Ethernet

7018 Series Fully Managed Gigabit Ethernet

• Eight 10/100BaseTX Ports

• -40ºC to 85º Operating Temperature

• Six 10/100BaseTX Ports

• Two 100BaseFX Ports

• -40ºC to 85º Operating Temperature

• Sixteen Ports

• -40ºC to 70º Operating Temperature

• Up to Eighteen Ports

• -40ºC to 70º Operating Temperature

Above Models Include:

• Web Configuration including MAC and IP Routing Tables, DHCP Server with Option 82

• N-Link Redundant N-Ring Coupling• SNMP V3• High Voltage Options Available

IN09Q3_08_09_Packets.indd 9 7/16/09 9:47 AM

Powering field devices such as sensors or controllers has been one of the interesting puzzles posed to plant engineers and network developers. and then, along came Power over ethernet (Poe).

while standardization as ieee 802.3af helped to drive acceptance and create interoperability, the non-standard proprietary innovations have continued to push it to its full potential,

whether industrial applications need it or not.Poe is being used mostly in robotics and some

machine applications where routing any cable is a problem and in vibration-prone applications in machines, says doug erlemann, business development manager-cameras for Baumer group (www.baumergroup.com). “one less cable is worth the slightly higher cost of the Poe system,” he says.

while most recognize the technology, Poe is still rarely put to good use in the industrial space, says eric Juillerat, president and ceo of raven Technology group (www.raventechllc.com). “ethernet has been fully accepted as a networking bus, but it remains clouded by decades of antiquated, in-place instrumentation and proprietary manufacturer buses, despite the massive availability of ethernet infrastructure solutions.”

ieee 802.3af defines the power sourcing equipment (Pse) and the powered device (Pd) that are used. a Pse is a separate device typically installed in the wiring closet near the ethernet switch or hub, explains gerard nadeau, Poe consortium manager at the university of new hampshire’s interoperability lab (www.iol.unh.edu) in durham, n.h. The Pse inserts dc voltage onto the twisted-pair cable and can be either an endpoint or a midspan device. an endpoint Pse is one that contains both the data communication capabilities and the power-delivery mechanism. a midspan only contains the power delivery mechanism and is inserted in the network between the legacy, non-Poe-capable ethernet switch and the Pd, explains nadeau. The midspan provides the ability to add Poe to the network without replacing the existing infrastructure.

The Pse chooses which mode and class of

service, or power level, it supports, explains art felgate, product manager, Transition networks (www.transition.com). “a Pse can support only class 1 and class 2 in Mode a, for example, and still be compliant with the ieee 802.3af standard,” he explains. class 1 requires at least 4 w of power, while class 2 requires 7 w. “if an attached Pd required greater power than class 2, this solution wouldn’t work, even

though both the Pse and Pd in this case are ieee 802.3af-compliant,” adds felgate.

classification of Pds should improve, adds felgate. “currently, many Pds simply indicate class 0 compliance—full power, up to 13 w—whether or not they actually draw that much current,” he says. “Many Pses can make intelligent decisions about managing their pool of power, if they have more accurate Pd power information. By providing a more accurate power signature during the Poe classification stage, Pds can contribute to more efficient use of network resources, especially power supplies.”

daisy-chaining is allowed by Poe, explains daniel feldman, Poe/Poe+ subcommittee technical chair of the ethernet alliance (www.ethernetalliance.org) and director of marketing for Microsemi (www.microsemi.com). “one could build a system that receives and then forwards power to another device, which receives power and forwards power and so on,” he says. “Practically speaking, one could daisy-chain four devices, extending the range of an ethernet cable up to 1,200 ft—four devices with 300 ft of cable each.”

ethercat uses only midspan power sources connected via cat. 5 cable directly to the power over ethercat device, explains Joey stubbs, Pe, PMP, north american representative, ethercat Technology group (www.ethercat.org). “These devices have only one connector, which prevents the cascading or daisy-chaining of additional devices to the network, so as not to exceed the 802.3af current and power limitations,” he says.

Midspan devices can be used to overcome switch limitations, including non-support of Poe or non-support of the maximum power requirement of the end device, explains Paul

b a n d w i d t h

Power to the Field Devices, Right Oninteroperability, as

with all technology,

is a concern for

poe, especially

with proprietary

midspans that

support 1000base-t

connections, which

aren’t compliant

with the ieee

standards.

Mike Bacidoremanaging editor

mbacidore@putman.net

industrial networking

Q3 • 200910

b a n d w i d t h

IN09Q3_10_11_Bandwidth.indd 10 7/16/09 9:49 AM

b a n d w i d t h

Brooks, business development manager, networks portfolio, Rockwell Automation (www.rockwellautomation.com). “Users should consider the function midspan devices perform and understand they aren’t required to be located near the switch,” he says.

As some manufacturers deviate from IEEE standards and seek new ways to raise the limits of power delivered over Ethernet, caution and application ultimately will set the bar.

Interoperability, as with all technology, is a concern for PoE, especially with proprietary midspans that support 1000Base-T connections, which aren’t compliant with the IEEE standards.

Some vendors are making proprietary midspans that support 1000Base-T, but since the designs aren’t standardized, this could lead to the kinds of interoperability problems that Ethernet solved long ago, explains Nadeau.

“Because they aren’t standards-compliant, there’s a risk they won’t work with equipment designed to meet the forthcoming POE+ standard,” says Felgate.

Relying on IEEE 802.3 standards is advantageous and ensures that PoE devices are not vendor-specific, says Stubbs. “It prevents a user from being locked into proprietary, expensive solutions from a single vendor,” he explains.

Nadeau agrees that the IEEE standard provides a greater potential for interoperability between vendors but notes that peace of mind creates limitations. “The disadvantages of being IEEE-compliant are that you might not be able to squeeze all the power out of the system and that you’re only allowed to power on one pair set at a time,” says Nadeau. “Proprietary systems tend to push the limit and could power multiple pair sets at one time.” However, this could cause interoperability problems and potential safety issues, he warns.

Due to the current large installed base of IEEE 802.3af solutions, manufacturers have an incentive to maintain compliance, notes Felgate. “The disadvantage of relying only on the standard is this may stifle adoption of some of the more interesting variations and uses of PoE,” he argues. “If

an organization has a compelling need or requirement to deviate from the standards, it should be fully aware of any risks that might entail.” Gigabit, for example, was left off of the scope for IEEE 802.3af-2003 for midspans, says Feldman. “IEEE 802.3at-draft4.2 addresses this issue,” he says. “If the specific midspan you have in mind

meets IEEE 802.3at-draft4.2 requirements, you should have no issues.”

As long as devices comply with the IEEE 802.3 standards, no problems should arise, adds Juillerat. “In mixed environments, the devices might need to be backward-compatible or support mixed media or port configurations,” he concludes.

1111industrial networking

Q3 • 2009

ASIA PACIFIC | AFRICA | EUROPE | MIDDLE EAST | L ATIN AMERICA | NORTH AMERICA

www.prosoft-technology.com/cogWhere Automation Connects™

+1-661-716-5100

Simple.Easy to install and easy to use.

Smart.Cost-effective solutions get your application running with unlimited Technical Support that keeps it running.

Seamless.Reliable, field-proven solutions that allow connectivity between diverse networks and controllers.

Protocol InterfacesProSoft Technology® is your single source for protocol interface solutions including Modbus, PROFIBUS, HART and many more.

Wireless TechnologySave on cabling costs and improve operational efficiencies with ProSoft Technology’s wide range of wireless solutions.

Put ProSoft in the Middle.

If you want connectivity that is...

IN09Q3_10_11_Bandwidth.indd 11 7/16/09 9:49 AM

Wireless communication in industrial facilities has moved decisively to become a practical solution. Practicality for industry means saving money without taking undue chances, and wireless has advanced to the point where it delivers concrete benefits with manageable risk.

the most obvious cost savings for wireless are delivered in installation, especially for projects in existing plants. it takes lots of money and time to dig trenches, lay conduit and pull wires. even for above-ground installations, the costs of conduit and wiring often are substantial.

savings over and above lower installation costs are realized during operations because of reduced maintenance costs and greater flexibility. Wireless is cheaper to maintain because there are no wires or cables that can be damaged. Wire and cable damage can occur through accidents such as lightning strikes, contact with moving in-plant equipment and inadvertent cutting during unrelated construction activities.

By Dan HeBert, Pe,

Senior tecHnical eDitor

inDuStrial networking

Q3 • 200912 e v a l u a t e

IN09Q3_12_15_CoverStory.indd 12 7/16/09 9:52 AM

13IndustrIal networkIng

Q3 • 2009

Normal wear and tear of wire and cables is most prevalent with connected components that move, such as those mounted on cranes, material-handling equipment and robot arms. Wiring and cabling to both moving and stationary components also can suffer wear and tear through corrosion, insulation breakdown and degradation due to temperature changes.

Another key advantage of wireless is flexibility. Once a wireless network is installed, the cost of adding another device is very low. Need an extra I/O point 2,000 ft from the control room? No problem with wireless, but very expensive with a wired system.

Wireless saves costs during installation and throughout the operational life of the control and monitoring system, but these savings are accompanied by the risk of implementing what for many is a new technology. Many users get around these risks by limiting the scope of the wireless system in terms of bandwidth, criticality and other parameters.

Cheaper to InstallIn most instances, it’s cheaper to install a wireless system than its wired counterpart. “We were hired by a major steel producer in the midwestern U.S. to replace the DCS controls on four large boilers that supplied steam to its steelmaking process,” says Timothy Stout, PE, manager process systems for system integrator Matrix Technologies (www.matrixti.com) in Maumee, Ohio. “Wireless saved money because it replaced very long conduit and cable runs of up to 2 miles. This saved miles of conduit and wire, which equates to several hundred thousand dollars in installation costs.”

Another long-distance application that resulted in substantial savings is detailed by Michel Dubé, automation coordinator at the Montreal facility of Para-Chem (www.parachem.com), a manufacturer of coating, emulsion polymers and adhesives. “We implemented remote monitoring with security cameras via a Wi-Fi wireless system. The monitored site is 1.2 km away from our security office, so we saved an estimated $200,000 Canadian on fiberoptic cables and installation,” relates Dubé.

Another remote application shows the savings realized with wireless. In this case, at Givaudan’s facility in Pedro Escobedo, Mexico, an Emerson Process Management DeltaV control system is being implemented in two areas separated by several miles of rugged terrain. “A Wi-Fi bridge will connect the two areas into one larger control system, saving the customer the cost of trenching and laying a fiberoptic cable between the two sites or having to construct two control rooms,” explains Neil Peterson, services manager for Smart Wireless at Emerson (www.emersonsmartwireless.com). Givaudan (www.givaudan.com) is a company in the fragrance and flavor industry.

The company is expanding a control system to manage three new reactors used to manufacture base products for fragrances. These reactors will be operated and controlled over a redundant wireless communication link from a new remote control room separated from the existing control room by 500 m.

Wireless also can save money on a smaller scale. “We have used wireless to connect portable and stationary label printers,” notes Harry Pettit, manager of systems and infrastructure engineering at Pepperidge Farm (www.pepperidgefarm.com), headquartered in Norwalk, Conn.

“Wireless provides flexibility in equipment location that you don’t get with hardwired, and we also estimate installation savings at $1,500 per printer,” adds Pettit.

Wireless not only saves money on installation labor, it can cut design costs. “With wireless, engineers don’t need to sort through rolls of schematic diagrams, installation and termination details and the drawings for the fabrication and layout of the cable tray, conduit, junction boxes and interface panels,” observes Joe Bingham, president and CEO of system integrator AES Global (www.aesglobal.com), Anaheim, Calif.

operatIonal easeThe central wastewater treatment plant of Lapuan Jätevesi Oy, in Lapua, Finland, treats household and industrial wastewater (Figure 1). The original automation system from 1992 was replaced in 2008 with new controllers, SCADA software and a wireless communication network in a project with Schneider Electric and system integrator Seinäjoen Teollisuussähkö Ky.

About 2,000 process variables are transmitted over the wireless network, and the network also is used for programming and maintenance purposes. A number of locations had to be linked as the control system has six controllers located in different buildings along with two control rooms.

SCH

NEI

DER

ELE

CTR

IC

Figure 1: a wireless ethernet system links six controllers and two control rooms at this wastewater treatment plant in Finland.

6 + 2 = WIreless

IN09Q3_12_15_CoverStory.indd 13 7/16/09 9:53 AM

IndustrIal networkIng

Q3 • 200914

From the user point of view, the main advantage was the cost and time savings for the installation as there was no need to dig trenches or modify existing cable paths.

From Seinäjoen’s point of view, the wireless RadioLinx network was the easiest part of the implementation. It didn’t have any problems, as the radios are very easy to configure and mounting recommendations given by radio supplier ProSoft Technology were very clear, says Seinäjoen’s. Schneider Electric made some tests and then explained how to implement the wireless network in the field.

MAINTENANCE REDUCTIONSWireless technology can help manufacturers reduce the skill set required for maintenance tasks. “Most maintenance issues are mechanical problems,” observes Cliff Whitehead, manager of strategic applications at Rockwell Automation (www.rockwellautomation.com).

“Rather than alert a highly skilled, high-cost controls engineer for every fault, manufacturers can alert locally based mechanical technicians,” explains Whitehead. “These mechanical technicians are better- equipped to solve the majority of problems but sometimes need the support of controls engineers. To accomplish this, manufacturers can make a wireless cellular modem part of the mechanical toolbox to create a connection that is locally manned by mechanical technicians and remotely manned by centralized controls engineers.”

Wired systems not only experience wiring and cable failures, but also other problems linked to hardwiring. “Wired instrumentation tends to get damaged through power spikes in the system that can burn out analog input channels,” observes AES Global’s Bingham. “These defects are difficult to troubleshoot, but burnt analog input channels are a thing of the past with wireless instruments, and the loss of the instrument is easily detected through the loss of communications.”

e v a l u a t e

wireless is a natural fit in applications such as robot arms where I/o must be connected to moving parts. Motion Controls robotics (www.motioncontrolsrobotics.

com) provides full-service robotic solutions to customers worldwide from its 57,000 ft2

facility in Fremont, ohio. one of its customers, a manufacturer

and marketer of paper and plastic disposable packaging for the food service industry, needed a robotic system to palletize cases of product. the system consists of five robots, each mounted on a 50-ft rail system. At the end of the robotic arm is a tool with eight double-solenoid valves and one photo eye sensor, requiring 16 outputs and one input.

to provide adequate wired I/o, the system would require expensive high-flex cable the length of the rail system along with soldering three separate connection points with approximately 20 wires per connection. working with Phoenix Contact (www.phoenixcon.com), Motion Controls robotics found a solution that instead uses Bluetooth wireless.

the PlC that controls the overall system connects via ethernet/IP cable to a bus coupler. the coupler connects to five Bluetooth wireless I/o base stations

located nearby. each of the base stations then connects wirelessly to two Bluetooth wireless I/o devices mounted on each of the robotic arms, located 80-120 ft away from the base stations. each of the I/o devices has eight inputs and eight outputs.

the bus coupler, the five base stations and the 10 Bluetooth-enabled I/O modules all are housed in IP65/IP67 blocks for direct machine mounting. unlike wi-Fi, which also uses the 2.4 GHz spectrum, Bluetooth uses the frequency-hopping method of spread-spectrum wireless that results in higher energy per bit and punches through any noise floor present. these hops occur 1,600 times per second, so when a packet is lost to interference, the next transmission is sent 625 μsec later.

Eric Hohman, PLC programming and systems design engineer for Motion Controls robotics, says wireless I/o eliminated about 20 hours of wiring and soldering per robot.

“wireless eliminated two separate cables in two different areas that are continually flexing,” observes J.P. Yeager, electrical designer for Motion Controls robotics. “the lifespan of these types of cables can be several months to several years, but eventually they fail and require time-consuming replacement.”

A wireless bridge connects I/O at the end of this robot arm to a central controller. The robot is used to palletize boxes.PH

OEN

IX C

ON

TAC

T

I, RObOT; YOU, WIRElESS

IN09Q3_12_15_CoverStory.indd 14 7/16/09 9:56 AM

15 INDUSTRIAL NETWORKING

Q3 • 2009

Not only does wireless save money during ongoing operations, it also can be safer. “Wireless improves safety by simplifying monitoring, modification and upgrades,” says Robert Konermann, product marketing manager for automation and safety at Schneider Electric (www.schneider-electric.us). “This can be significant with electrical panels containing high-voltage equipment, particularly when water or other hazardous conditions are present. Because of the wireless network, workers don’t need to be in physical contact with the panel or open the panel doors to expose the wiring, components or live equipment.” Long-term savings are abundant due to the fl exibility of wireless, which makes it easy to add, replace or modify components, adds Konermann.

WHAT’S HOLDING WIRELESS BACK?Wireless works in the right application but, like any technology, it has limitations. “Wireless has its place when you can get by with gaps of missing data or when you have diffi culties in getting wiring to sensors or I/O,” says Gary Crenshaw, electrical engineer at Beam Global Spirits and Wine (www.beamglobal.com) in Clermont, Ky. “But I don’t see wireless replacing all control system hardwiring. Cell phones are some of the best wireless devices we have, but they are not 100% reliable. � ey are dependable enough to be very useful, but they can’t be counted on in an emergency.”

THEN, THERE’S THOSE STANDARDS� e lack of standards for wireless has delayed implementation, but this is improving. “Wireless standards such as IEEE 802.11 will improve user confi dence because its spread-spectrum modulation techniques are less susceptible to interference,” argues AES Global’s Bingham. “� e ISA 100 wireless standard helps make implementation easy due to wide acceptance in the instrumentation and automation industries.”

Vendors and industry organizations are jumping on the standards bandwagon. “At one time, we expected to create a Profi bus process wireless standard,” comments Carl Henning, deputy director for Profi bus and Profi net in North America (www.us.profi bus.com). “But, with the release of WirelessHART, we realized that was no longer necessary. Instead we formed a cooperative team with the Fieldbus Foundation and the HART Communication Foundation to simplify access to WirelessHART from our respective technologies,” adds Henning.

Standards already promote use in some applications. “ISA 100 compliance was a key factor in selecting Honeywell for our project,” comments Para-Chem’s Dubé. “The standard will allow us to add wireless devices from many different suppliers in the future, and these additions will show much higher payback because the wireless infrastructure is already in place.”

Wireless becomes almost a necessity when long distances need to be traversed to reach a mobile location like an oil drilling rig. “We had a project that required connection of a device used to monitor the amount of gas produced by a drilling operation,” says Lee Hilpert, president of system integrator HilTech (www.hiltecheng.com) in Tomball, Texas.

“The sensors and instrumentation are several hundred feet from the area where the data is needed. In addition, the drilling rig moves about every 45 days. Without wireless, it would be necessary to dig a trench, bury conduit to run a communication cable, pull and terminate the communication cable and hope nobody compromises the cable during the drilling process. With wireless, you set it up and turn it on, and installation takes less than a man-hour.” With a wired installation, you’d then have to disconnect, pull wire, remove the conduit and remediate the trench.

The two RF modems installed at the oil rig and at the system computer have some limitations. “The transfer rate is low compared to a wire or � beroptic system, but data exchange requirements also are low,” observes Hilpert.

He says the savings are signi� cant. “The wireless link costs less than $1,000,” says Hilpert. “The Digi 900 MHz modems are about $300 each and are essentially plug and play. Compare this to hardwiring where, at best, it’s going to take two men at least a day. ”

WIRELESS WELLS “WIRELESS HAS ITS PLACE WHEN

YOU CAN GET BY WITH GAPS

OF MISSING DATA OR WHEN YOU HAVE

DIFFICULTIES GETTING WIRING

TO SENSORS OR I/O.”

WIRELESS ADVANTAGES1. Cheaper installation2. No wear and tear on cables3. Easier to modify4. Better for mobile equipment applications

WIRELESS CHALLENGES & ISSUES1. Slow data transmission rates2. Dropped data packets3. Lack of experience among end users4. Con� icting standards

IN09Q3_12_15_CoverStory.indd 15 7/16/09 9:57 AM

IndustrIal networkIng

Q3 • 200916

FrustratIng obstacles and unexpected MysterIes oF a wIreless

network project aren’t covered In the Manual

Wireless: The Real World

The applicaTion of new Technologies seldom goes as planned and can be an outright adventure. But the potential for significant cost savings can make overcoming the hazards and pitfalls well worth the journey.

That was the case at our plastics plant in pasadena, Texas, where we needed to overcome obstacles and create a wireless system to monitor certain data readings.

initially, the impetus for the project involved the need to obtain two readings, but things escalated quickly. The equipment was installed in august 2007. design for the installation had started earlier, in february.

the Wireless OppOrtunity we use a 40-ft-tall api tank when we unload a barge. each time, the operator would climb the tank to record temperature at the vent and vent valve position after the tank’s condenser unit. The plant wanted to automate the recording of measurements to record the vent temperature and vent valve position to provide improved

documentation for our environmental records and improve operator efficiency by eliminating the time-consuming, lengthy, repeated trek to the top of the tank (figure 1).

Because the process variables we wanted to measure were at the very top of this tank, it would have required a long cable and conduit run up the side of the tank. it would have required a 40-ft-tall scaffold to run the conduit and cable. The costs to obtain just two new readings didn’t seem justified compared to a traditional hardwired method.

“we began to look at a wired solution,” says John scott, senior account manager from the Rosemount division at emerson process management (www.emersonprocess.com), “but we came up with a 65% installation savings by going wireless. one of the bigger costs for a wired solution would have been the scaffolding.”

wireless obviously was the best choice. we looked at several wireless network solutions, but determined that emerson was a good choice for this plant. Regular-style wired Rosemount transmitters already were used at this unit. Training on the handheld was up-to-date. This meant that training only needed to cover troubleshooting changes due to the wireless hardware and setup. This would minimize our training costs, as well.

Wireless netWOrk Designwe began to seriously explore implementing a wireless solution to this problem. one concern was how to provide valve position. emerson didn’t offer any direct valve-positioning transmitters except as an add-on to the digital valve positioner. The controller for tank pressure was a local pneumatic controller with a pneumatic valve positioner. i eventually realized that i could use a pressure transmitter on the controller output and provide an implied valve position.

designing a wireless network, to my interpretation, meant that cable runs were kept to a minimum, reducing both installation and material costs. it seemed, therefore, that the best location for the wireless gateway would naturally be on top of the rack room (figure 2). i could easily interface with the old provox dcs equipment via the intelligent device interface module set to accept modbus and run only three short cables—modbus, ethernet and power—to the roof.

This older version of the wireless network required that the distance to the gateway be less than 500 ft. The temperature and valve-position-measurement points were 600 ft away from the rack room. additional transmitters between the api tank and the rack

by alIce McwIllIaMs, pe, chevron phIllIps

I M p l e M e n t

FiguRe 1: TO THe TOP OF THe TANK

eliminating the time-consuming, repeated trek to the top of the tank with a wired measurement solution would have required a 40-ft-tall scaffold to run the conduit and cable.

ch

eVRo

n p

hil

lips

IN09Q3_16_19_featr2.indd 16 7/16/09 10:15 AM

17IndustrIal networkIng

Q3 • 2009

room were needed to act as repeaters for the API tank data. These additional wireless applications between the API tank and the rack room would improve both distance and stability needs. Mesh wireless networks also become more stable as the number of nodes to the network increases. Fortunately, it was easy to find more readings that the plant wanted. The production engineers for our unit also were excited about trying a wireless network. Two additional measurement applications, the bearing temperatures for two pumps and the barge unloading line pressure, fell into our laps (Figure 3).

One of the pumps on a tank closer to the rack room had experienced bearing failure earlier that year, and caused a hydrocarbon leak into the electrical housing. Monitoring the pump bearing temperature would improve reliability and safety in this operation.

Also, our barge unloading line was experiencing pressure excursions in excess of what we would like. It wasn’t easy for the production engineer to tie the higher pressures with specific events during the unloading cycle. Most of the unloading valves were hand-operated, and the barge unloading information also was isolated to the dock area. The recorded pressure indication could help determine the point in the cycle when the high pressure occurred, so we could develop better procedures for preventing recurrence. Both of these applications were a great opportunity to bring information that would provide improved plant operation to the DCS. In the end, we planned to develop a wireless network consisting of five transmitters: tank vent temperature, vent valve position, two pump-bearing temperatures and barge unloading line pressure.

TransmiTTer UpdaTe-Time decisionsWireless transmitters don’t provide data at a very fast update rate. Emerson generally recommends update times around a minute. Pressure is a fast-changing variable, and I was particularly concerned about the slow update rate for the two pressure transmitters on the unloading line. What if, at a 1-min update rate, we totally missed recording the event that signaled the pressure excursions on the unloading line?

In the end, I picked 15-sec update rates for all the transmitters except the barge unloading pressure. I found out at installation that, although the recommended lower limit was 15 sec, the system actually could perform at much faster rates. I selected a 3-sec update rate for the barge unloading line pressure. The downside to changing to a faster update rate was sacrificing some battery life and gateway capability.

TransmiTTer VariablesThese days you can pick and choose what you feel is important

information from your transmitters and bring this data into the DCS. I heard and read a lot about battery life and battery voltage from Emerson’s experts and literature. I decided that, besides the main transmitter variables, I also would bring in the battery voltage as an additional variable for each transmitter. This turned out to be a good decision. Now I regularly review the battery voltages, and we created an alarm to alert the operator when the voltage dropped too low.

WhaT aboUT radio inTerference?For the installation of a wireless network, another hurdle needed to be cleared. Our plant radios use the same 900 MHz frequency range as the network. The radios provide critical communication for our operators, especially if an abnormal situation should develop in the plant. Our radio group was very concerned about a network that would run at the same frequency as the plant radio system.

We held two separate in-plant trials using Emerson sales-demo units. During the second trial, the radio group brought its frequency analyzer. It showed no interference. However, they still were not completely comfortable, and wanted us to wait until the 2.4 GHz wireless transmitter network was available. To put their minds at ease, Emerson’s Scott explained five key aspects employed by the network security, including protection/encryption, authentication, verification, key management and anti-jamming. That satisfied their concerns.

figure 2: uP ON THe rOOf

The gateway on the rack-room roof was difficult to access, which was discovered when the first gateway developed mold on an electrical card before the network was even launched in august 2007.

CH

EVRO

N P

HIL

LIPS

our radIo group was very concerned about

a network that would run at the same

frequency as the plant radIo system.

IN09Q3_16_19_featr2.indd 17 7/16/09 10:16 AM

IndustrIal networkIng

Q3 • 200918

Mind the detailsBy July 2007, I was reviewing the installation by our on-site construction team. At this point, I realized that none of the transmitters had batteries installed. Apparently, the batteries were delivered separately and without a specific line on the purchase order (PO). The receiving department didn’t have the means to handle a delivery that didn’t match to the PO. All the new batteries were lost and never located. The planned imminent installation by the Emerson team was delayed several weeks while the batteries were reordered and delivered.

Gateway troublesSince the gateway and antenna were married together, I thought putting the gateway on top of the rack room to receive signals from all different directions within the plant would be a good idea. Unfortunately, the roof was difficult to access. We discovered how inconvenient a location this was when the first gateway developed mold on an electrical card before the network was even launched in August 2007. Emerson replaced the gateway under warranty. The second gateway quit in November 2007, a little more than two months after it was installed.

Then, one day all the points started drawing straight lines. I had five or six irons in the fire that day. So, rather than call Emerson’s tech support, I cycled power in the hope of resetting it. Due to the lack of any luck at all, that action vaporized all stored data on what had gone wrong with the gateway. The failure of this gateway, after post-mortem analysis, again pointed to the radio card. Emerson again replaced the gateway under warranty and lent its demo unit to us until the warranty replacement gateway arrived.

When the third gateway came, it included a remote antenna.

This was a feature I had wanted from the start, but it only recently had become available. Getting the gateway down from the roof and adding the antenna made a huge difference in troubleshooting accessibility. Finally, the wireless gateway with remote antenna was installed and operational. It seemed things were looking up.

wireless MysteriesThe temperature transmitter on the very top of the API tank—the sought-after measurement that started this grand adventure—was the first one to give me trouble. One lovely day in December 2007, the outside temperature was 70 °F. The next day the temperature plummeted

to 35 °F. This transmitter provides the condenser temperature reading that was the cornerstone of the whole wireless network project. Examining trends of the battery voltage showed 6.84 Vdc on Dec. 15 and 5.56 Vdc on Dec. 16. Somewhere around 5.5 Vdc is the point at which the transmitter stops functioning. I was very surprised to have a battery failure after only four months of operation. From what I had discerned from the vendor literature, I expected these batteries to last for years. I hadn’t expected to need spares so soon.

Emerson brought a replacement battery, and soon we were back in operation, but I continued to be puzzled by the battery failure. Obviously, these batteries developed lower voltages in the colder weather. I tried without success to procure some sort of graph or formulas to determine battery life. Battery life apparently was meant to remain a mystery to all users.

Mysteries continued with a new slant. My important API tank condenser temperature transmitter suddenly stopped transmitting on March 6, 2008. Sixteen hours later, before I could even determine that it had gone nonfunctional, the transmitter resumed sending data. Did something get in the way of the radio signal and break the path?

The condenser transmitter had two communication paths to the gateway: one directly to the gateway (600 ft) and another relayed through the valve-position pressure transmitter (5 ft away). This transmitter was on top of a 40-ft tank, and the pressure transmitter that it communicated with most reliably continued transmission of its data throughout this episode. Battery voltage was not an issue. The voltage when the device quit communicating was 7.08 Vdc. Emerson performed an on-site mapping of the wireless network system operation through the 1420 Gateway. However, this offered no clues to what caused this mysterious signal loss. This same event occurred on this condenser temperature transmitter later in 2008. This time, the transmitter was rebooted to start communicating by pulling out the battery and putting it back.

I m p l e m e n t

figure 3: MeSH NeTWOrK

additional transmitters were needed to act as repeaters. Mesh wireless networks also become more stable as the number of nodes to the network increases.

CH

EVRO

N P

HIL

LIPS

I decIded that I also would brIng In

the battery voltage as an addItIonal

varIable for each transmItter. thIs

turned out to be a good decIsIon.

IN09Q3_16_19_featr2.indd 18 7/16/09 10:16 AM

19IndustrIal networkIng

Q3 • 2009

I again contacted Emerson to glean some additional insight into why this transmitter would lose contact with the wireless network. They offered to repeat the system mapping that had been done earlier. I declined the offer since it required taking the whole network down for an hour or so, and the process had yielded nothing to help previously. They did suggest trying the antenna on the transmitter at a different angle. We implemented this suggestion, and the condenser temperature transmitter has remained in communication since that date.

Trouble When WeTThe batteries, however, were not finished plaguing me. On April 28, 2008, one of the pump-bearing temperature-transmitter batteries dropped to 5.37 Vdc during an ambient temperature swing of approximately 20 °F down to 58 °F, the point at which the transmitter failed high. This battery was replaced after a life of about one year.

I was confused. Where were the years of battery life that the literature talked about? At Emerson’s conference in October 2008, I discussed battery life with any Emerson expert who would listen. One of these experts told me that one year really was what might be expected with an update time of every 15 sec. I keep looking

for that chart where I actually can calculate battery life myself.

At one point, given our concern about losing signals and batteries, we removed the transmitters’ covers and found some of them had condensation on the batteries. The first thought was: “Wow. This is the source of our problems.” The recommendation was to put Teflon tape on the conduit plugs to discourage any outside air exchange with Houston’s humid weather (Figure 4). Little details often make the difference. However, it’s difficult to prove whether this made a big difference in our battery life because this pump bearing temperature transmitter is not done with me yet. It failed again on May 18 and again a month after that. It turns out this was a good transmitter gone bad—a transmitter that ate batteries. Emerson provided a replacement under warranty, and there have been no failures since.

AdvenTure lessons leArnedWith all of these lessons came a lot of valuable experience, not the least of which was the skill set we developed troubleshooting wireless. Plus, we added the temperature transmitter ourselves, without Rosemount, to prove the system is easy to maintain and grow. We also got a lot of valuable process information at a much lower cost due to the 65% installation savings. The barge-unloading pressure did provide the information needed to determine improved operation practices. And, when Hurricane Ike hit in September 2008, the network kept running without a hitch right through all that extreme wind and rain.

Alice McWilliams, PE, is senior instrument and controls engineer at Chevron Phillips (www.cpchem.com) in Pasadena, Texas.

Figure 4: STiCKY SiTuATiON

houston’s humid weather caused water to accumulate beneath the transmitters’ covers, which necessitated Teflon tape on the conduit plugs to discourage outside air exchange.

CH

EVRO

N P

HIL

LIPS

SeaI/O Control Design-Industrial Networking

1/3page square 4 9/16” by 4 7/8”

We Listen. Think. And Create.

F CUSOn Success

HMISerialI/O

Industrial Computing

DigitalI/O

DistributedI/O

SeaI/O Solutions Offer: • Digital & Analog I/O• Connection via Ethernet, USB,

RS-485, or RS-232 • Daisy Chain Expansion • Field Removable Terminal Blocks • Compact, Rugged Form Factor • DIN Rail or Table Mount Design• Robust Development and

Con guration Tools

Create a powerful distributed data acquisition

system with Sealevel’s SeaI/OTM family of digital

and analog control modules.

IN09Q3_16_19_featr2.indd 19 7/16/09 10:17 AM

IndustrIal networkIng

Q3 • 200920 r e s e a r c h

SNMP CONVERSIONBradcommunications 200 Series Direct-Link industrial Ethernet unmanaged switches are equipped with five-, eight- or nine-port switches and are plug and play. Other features include auto-sensing, auto-polarity and auto-crossover. Each is DIN-rail- or panel-mount and equipped with redundant, dual dc power inputs. The 300 Series managed switches are equipped with IGMP snooping, VLAN and QoS for prioritization and support redundant ring network technology and advanced network management. Direct-Link SNMP Management Suite converts SNMP messages into OPC tags that can be incorporated into and portrayed by HMI OPC client software.Molex; 800/786-6539; www.molex.com

WORKGROUP SWITCHMach10019-in. rack-mount switches operate 0-50 °C without fans. The switches include two Gigabit RJ45/SFP combo ports and are offered with either eight or 24 permanently installed 100 Mbps ports or as a modular device with eight ports and slots for two other eight-port media modules. These modules, which

are designed for 100 BaseTX, 100 BaseSFP or 100 BaseFX (multimode and single-mode), can be changed during operation by means of a hot-swap function.Hirschmann; 717/217-2200; www.hirschmann-usa.com

NOISE IMMUNE SWITCHEKI-4654R is an IEC 61850-3-compliant managed Ethernet switch for grid automation applications. IEC 61850-3 certification ensures environmental and EMI immunity. The switch features 24 10/100BaseT Ethernet ports and two 1000BaseTSFP slots. It has a wide range of redundant power inputs, allowing connection to two separate power supplies and guaranteeing operation in the event one source goes off-line. The switch supports X-Ring, standard Spanning Tree and Rapid Spanning Tree protocols.Advantech Industrial Automation Group; 800/205-7940; www.advantech.com/ea

SMaRT SWITCHESStride line has been expanded to include industrial-grade unmanaged Ethernet switches and media converters with aluminum housings. Designed for wide-temperature (-40 to 85 °C) applications, these true plug-and-play devices automatically determine and remember devices connected to each port and only route messages through the appropriate ports, increasing speed and

bandwidth. Even under heavy I/O and data exchange, Stride switches and the Ethernet control network maintain more consistent cycle times.AutomationDirect; 770/889-2858; www.automationdirect.com/ethernet

routers and swItches contInue to Manage and dIrect data on

the network InforMatIon hIghway

The Once and Future Network Traffic Cops

AS MORE INDuSTRIAL DEVICES wITH BuILT-IN ETHERNET capabilities are introduced, networks will become more complex and crowded with signal traffic. “This will increase the need for Ethernet switches and routers with advanced functionality that can limit collisions, control bandwidth and create virtual local area networks (VLANs),” says Chris Vitale, senior product manager with Turck’s network and interface division (www.turck.com).

“An advantage of today’s LAN switches over earlier LAN hubs and repeaters is the presence of microprocessors in the switch to selectively direct communications from one remote device to another,” explains Jim McConahay, PE, senior field applications

engineer for Moore Industries International (www.miinet.com).“with switch technology improving, we will see a greater emphasis

on the built-in intelligence, which will allow someone who is well-trained in Ethernet to make dramatic improvements to their device communications,” says Erik Syme, technical support manager at ProSoft Technology (www.prosoft-technology.com).

“Ethernet routers and switches will not go the way of hubs and repeaters today because they provide industrial engineers with two valuable items, control and flexibility, whereas hubs and repeaters only provided connectivity,” explains Bruce Hofmann, director of marketing, weidmüller North America (www.weidmuller.com).

IN09Q3_20_23_Research.indd 20 7/16/09 11:24 AM

21IndustrIal networkIng

Q3 • 2009

Messaging ModuleMessage Manager ILX56-MM module is a multi-system data transfer engine that resides in a single slot of a ControlLogix chassis. The module enables PLC-to-PLC data transfer without requiring message programming or ladder logic. The module is configured using a built-in graphical Web-based configuration tool with user prompts. Data transfers can be set up by users at one location for up to 16 different Rockwell Automation and Siemens controllers.ProSoft Technology; 661/716-5100; www.prosoft-technology.com

siMple Managed switchIndustrial Ethernet ring switch offers the performance features of a managed switch with the simplicity of an unmanaged switch. The switch comes preconfigured for ring redundancy, offering virtual plug-and-play performance, and it uses self-healing ring topology. The switch

provides the port mirroring, broadcast storm protection and priority queuing of a managed switch. In addition to offering fast recovery time of 30 msec + 5 msec/hop, the switch allows for real-time data transfer with IEEE 802.3 Ethernet compliance. Ultra Electronics; 512/434.2850; www.ultra-nspi.com

First Fisco FieldbusRoute-Master Fieldbus System has a new ATEX approval (FM pending) as a redundant intrinsically safe fieldbus system, permitting the connection of any mix of FISCO and Entity devices. This is the first fieldbus system approval to offer FISCO compatibility and power redundancy. A Route-Master system consists of up to eight trunk isolator modules in a 19-in. rack, each connected to one or more RM100 fieldbus device couplers. Moore Industries-Int’l; 818/894-7111; www.miinet.com

sync your clocksEL6692 EtherCat bridge terminal improves synchronization for highly complex machines and production lines with numerous EtherCat masters. In the most complex systems, data may have to be exchanged between individual EtherCat systems, or the distributed clocks of different systems may have to be synchronized. The bridge terminal

is an ideal solution as it cost-effectively implements these tasks directly in the I/O system. In addition to normal data exchange, the EtherCat bridge permits distributed clock synchronization.Beckhoff Automation; 952/890-0000; www.beckhoffautomation.com

poe switchFully managed, eight-port PoE switch is designed to power network devices intelligently and enable PoE infrastructure via fiber. The ruggedized device comes with built-in dual fiber uplinks and is backed by a lifetime warranty. The SISPM1040-182D-LR(T) provides fiber connectivity and can power wireless access points. All RJ45 ports support Auto-negotiation and AutoCross, and all SFP ports support both 100BaseFX and 1000BaseXSFP optics. The eight RJ45 ports w/PoE fully support the IEEE 802.3af standard, providing a full 15.4 W to as many as eight devices.Transition Networks; 800/526-9267; www.transition.com

alarMing switch852 series Ethernet switches offer an alarm contact, enabled via dip switch, to signal an error condition on the switch. The power

input connector on the switch has two dedicated alarm circuit connections that can be wired to any warning device, such as a PLC. Error conditions that can be monitored include port link failure, power supply disruption/disconnect or power supply voltage out of specified range.Wago; 800/din-rail; www.wago.us

entry-level switchScalance X family of industrial Ethernet switches has been expanded to include the simple-to-use, space-saving and affordable Scalance XB. The entry-level Scalance XB unmanaged industrial Ethernet switch can be used in a line or star topology where simple plug-and-play connections and low-cost port expansion features are required. The Scalance X family of switches are available with up to eight 10/100 Mbps ports.Siemens Energy & Automation; 800/241-4463; www.sea.siemens.com

Multi-port switchesEK series of rack-mount industrial Ethernet managed switches are offered in 26-port and 32-port models. These switches are industrial-rated and designed to meet the requirements of power substations (IEC 61850/IEEE 1613), traffic control (NEMA TS2), railway applications (EN 50121-4) and maritime use (ABS/DNV/GL). The compact 1U rack-mount packaging fits into standard EIA, WECO and ETSI racks 19-24 in.Sixnet; 518/877-5173; www.sixnet.com

IN09Q3_20_23_Research.indd 21 7/16/09 11:25 AM

IndustrIal networkIng

Q3 • 200922 r e s e a r c h

USB HUBSFour-port and seven-port hubs are USB 2.0-compliant, providing 480 Mbps data rate to the host, and are backward-compatible with USB 1.1 and 1.0 devices. Each includes a wall-mount ac adapter that supplies 500 mA to each attached USB peripheral. Both hubs are housed in rugged plastic enclosures. The hubs are supported in Windows, Linux and other USB-aware operating systems.Sealevel Systems; 864/843.4343; www.sealevel.com

HigH-THroUgHpUT radio702-W industrial wireless Ethernet radio with IEEE 802.11n support allows the radio to use three antennas and multiple-

in-multiple-out (MIMO) technology for increased throughput, yielding much higher data rates than devices supporting only 802.11a/b/g. The radio supports 802.11a/b/g compatibility for existing wireless networks. Extended environmental specifications allow operation in temperatures from -40 to

70 ºC. Auto sensing 10/100BaseTX is included.N-Tron; 251/342.2164; www.n-tron.com

i/o HUB SySTemStandalone Ethernet hub system is part of the X20 slice I/O series. The modular design of the active hub allows it to be used as a 4x or 6x hub. The smallest version is a solution as a 2x hub for extending Ethernet sections up to 200 m. Besides standard Ethernet, the modular hub system can be expanded with an X20 bus controller module with an integrated 2x hub for Ethernet Powerlink.B&R Industrial Automation; 770/772-0400; www.br-automation.com

inTelligenT SwiTcHSmart Managed Compact Switch (SMCS) has eight ports capable of simultaneous Gigabit operation. SMCS is suitable for Profinet, EtherNet/IP and standard Ethernet applications. A version with eight twisted-pair ports and another with six twisted-pair and two

fiber ports are available. The switch’s integrated Web server provides access to switch functions and settings. It can be configured using the Web browser, simple network management protocol (SNMP) or a serial connection. Phoenix Contact; 800/322-3225; www.phoenixcon.com

gaTeway To deviceneTDeviceNet gateway joins gateways in BL20 economy system. The gateways provide a cost-effective solution to expand fieldbus I/O and connection of up to 32 I/O modules, including digital and analog, for a system that can handle 512 digital I/O points or 128 analog I/O points. A combination of digital and analog I/O on a single node is an option.Turck; 800/544-7769; www.turck.com

verSaTile SwiTcHEntry-level industrial-grade Magnum 6KQE Ethernet managed edge switch is compact and environmentally sealed for physically and environmentally constrained installations. Its modular design

supports up to 8 10/100TX and 2 GigE Ethernet ports, with configuration options for TX or fiber interfaces and optional power over Ethernet (PoE), as well

as several integral power supply options. The switch provides advanced networking features such as RSTP and VLANs, as well as management interfaces. GarrettCom; 510/438-9071; www.garrettcom.com

iT’S manageaBleStratix 8000 modular managed switch line with six to 26 ports includes the resilient Ethernet protocol (REP), DHCP per port and CIP sync protocol. It uses Cisco Catalyst switch architecture and feature set and can be configured using RSLogix 5000 programming software. It automatically generates Logix tags for integrated diagnostics. Switches have a removable compact Flash card.Rockwell Automation; 440/646-3434; www.rockwellautomation.com

aSi modUleSVBA-4E4A AS-Interface junction-box modules are 28.65 mm high and deliver 4-in/4-out functionality to support 62 nodes

per network. All I/O is powered directly by the AS-Interface module, eliminating the need for an additional power source. Industrial dual-lock mounting strips increase the total mounting height to 35 mm. Removable

terminals enable programming and module change-outs, and LED indicators help with troubleshooting. Pepperl+Fuchs; 330/486-0001; www.pepperl-fuchs.com

IN09Q3_20_23_Research.indd 22 7/16/09 11:26 AM

Secure routerSIndustrial Ethernet routers are designed to provide networking options and controls such as firewall protection, remote network access, virtual mapping of networks, virtual private networks, DHCP

server options, DNS server functionality and network callback features. The routers provide the tools and capacity for superior network security such as SSH tunneling, VPN, virtual mapping (NAT), port forwarding, port filtering and a packet-level inspection firewall. Weidmüller; 800/849-9343; www.weidmuller.com

extend the dataLDM heavy-duty modems extend the distances that computers, terminals and other devices can communicate in hazardous

industrial and institutional environments. Six models communicate over continuous dedicated wire pair and distances to 12 miles using standard RS-232/485 protocols. Two additional models feature fiberoptic data links for total electrical isolation and operation to 2 miles.Dataforth; 520/741-1404; www.dataforth.com

Iec 61850-3 coMPLIantPowerTrans IEC 61850-3 and IEEE 1613 compliant Ethernet switches protect against

electrical, EMI and other critical threats. Modular rack-mount design with high optical fiber and Gigabit port density make the switches suited for retrofitting existing stations or establishing networks for new substations. Layer 3 routing is supported for better performance on large-scale substation LANs.Moxa Americas; 714/528-6777; www.moxa.com

ethernet/IP to ProFIBuSAnybus X-gateway connects PC-based OPC-client applications through standard Ethernet networks and the X-gateway to all major fieldbus networks. The OPC connectivity

feature is available for 19 industrial Ethernet to fieldbus versions of the X-gateway family with more than 50 combinations to choose from. It enables PC-based OPC DA client application to access data of distributed field devices located in a fieldbus network without the need for a PCI fieldbus interface card.HMS Industrial Networks; 312/829-0601; www.anybus.com

MORE, MORE, MORE

Find more information about routers and switches from companies including Digi, GE Intelligent Platforms, Lantronix, Ledco, Omron STI and Saelig at www.IndustrialNetworking.net/Q32009research.

INdustrIal NetworkINg

Q3 • 200923

IN09Q3_20_23_Research.indd 23 7/16/09 11:26 AM

IndustrIal networkIng

Q3 • 200924 p r o d u c t s

MULTI-PORT JUNCTION BLOCKSM8 multi-port, IP67-rated junction blocks have three-pin M8 connectors (v3 style) in four-, six- and eight-port models. They allow multiple sensors to be wired to a single block with a single cable run back to a controller.Pepperl+Fuchs; 330/486-0001; www.pepperl-fuchs.com

PhONe hOMeGSM/GPRS serial modem provides global access to machines and systems via GSM connections. An integrated TCP/IP stack allows the implementation of simple control systems into the GPRS network. A pre-installed SIM card makes activation quick and easy. It features two digital alarm inputs via Combicon connector and one digital output via T-bus connector.Phoenix Contact; 800/322-3225; www.phoenixcon.com

TC SIGNAL CONDITIONeRS8920-500-DC and 8921-1250-DC signal conditioners are for applications where single-point, isolated thermocouple signal conditioning is required. 8920-500-DC is for Type J thermocouples with a range of 0-500 ºC. 8921-1250-DC is for Type K with a range

of 0-1,250 ºC. Both use linearization and cold junction compensation and provide three-way signal isolation.Calex; 800/542-3355; www.calex.com

TWIST AND ShOUTChainflex CF Robot shielded robot cable is designed for applications with high levels of torsion such as robots, rotary tables or spindle drives. The torsion-resistant tin-plated copper shield sheath has been tested through more than 3 million movements to ±270°.Igus; 800/521-2747; www.igus.com

PRINT TAGSPrintJet Pro ink-jet printer prints plastic markers in standard MultiCard format. 600-dpi print quality is designed for printing tags and markers for direct mount onto devices, cables, relays and

terminal blocks. Black and color print is produced using water-based environmentally friendly ink. M-Print Pro software is engineered to operate intuitively and can link directly to CAE/CAD systems. The controls panel is flush-mounted on the top of the printer and can be rotated 180° for ease-of-use. Weidmüller; 800/849-9343; www.weidmuller.com

SIGNAL CONDITIONINGTwo new signal conditioning modules are Adam-3112 and Adam-3114. The Adam-3112 is an isolated ac voltage to dc voltage module, while the Adam-3114 is an isolated ac current to dc voltage module. These two signal conditioning modules can convert up to 400 Vac or 5 Aac signals to 0~5 Vdc signals for data acquisition cards to measure while reducing the harmful effects of ground loops, field noise and electrical interference. Both modules provide 1,000 Vdc between output and power, as well as 2,500 VRMS between input and output and between input and power. The 3112 provides three input modes, 0~120 Vrms, 0~250 Vrms and 0~400 Vrms in one single signal conditioning module.Advantech, Industrial Automation Group; 800/205-7940; www.advantech.com/ea

WIReLeSS MONITORING SySTeMIndustrial-focused wireless monitoring solutions are designed for monitoring and controlling processes in difficult industrial and hazardous applications. Through a comprehensive system of transmitters, receivers, transceivers and interface gateways, these solutions offer both one- and two-way wireless monitoring. The product line is complemented by accessories including high-powered antennas for long-distance communications and explosion-proof enclosures for hazardous application. Each device offers a wide selection of digital, analog and pulse inputs that allow fewer radios per system.Cooper Crouse-Hinds; 866/764-5454; www.crouse-hinds.com

CONveRT MODICON TO A-BI/O wiring conversion system helps users migrate existing control platforms to the Allen -Bradley ControlLogix programmable

IN09Q3_24_25_Products.indd 24 7/16/09 11:46 AM

25IndustrIal networkIng

Q3 • 2009

IndustrIal networkIng

Q3 • 200925

automation controller (PAC). Users can now replace Modicon 800 Series I/O racks with the ControlLogix I/O system without disturbing field wiring. The swing-arm conversion system takes the existing Modicon 800 I/O swing arm and converts the field terminations to match a compatible ControlLogix I/O module. The ControlLogix I/O system allows users to keep the same panel footprint. Rockwell Automation; 800/223.5354; www.rockwellautomation.com/solutions/migration

INTERFACE MODULEDSUB series of DIN-rail-mounted interface modules provides a plug-and-play interface for industrial control systems, ideally in packaging and automated assembly. These

CE-compliant modules come with male and female D-subminiature connectors and are available as nine-, 15- and 25-pin models. Optional D-SUB cables are available. Specifications include 1 A maximum current, 22-14 AWG wire range and -10 to 50 °C operating temperature.Omega Engineering; 888/55-omega; www.omega.com

POE INJECTORSThree new four-port 802.3af PoE injectors address applications where multiple data/power connections are required. The BT-CAT5-P4 series injectors feature industrial-grade cast-aluminum housings and shielded RJ45 jacks for EMI suppression. BT-CAT5-P4-4848 ships with a 48 W power supply, and BT-CAT5-P4-4870 ships with a

70 W power supply. The standard model BT-CAT5-P4 doesn’t include a power supply but can be used with a user-supplied ac or dc power supply up to 60 V. L-Com Global Connectivity; 978/682-6936; www.l-com.com

SHDSL MODEMRuggedized 3231 managed SHDSL modem features a front-panel touchpad and extends industrial Ethernet connections

up to 9.4 km. Password-protected local and remote management options enable the device to work with any existing network management policy. The universal management solution includes SNMP monitoring, Telnet and Web management, plus troubleshooting via remote-loopback. FlexKey touchpad with backlit LCD provides the ability to configure with no tools or computer. The modem transmits data at 4.6 Mbps over distances up to 3.3 km.Patton; 301/975-1000; www.patton.com

25

a d I n d e x

ContaCt us555 W. Pierce Rd., Suite 301, Itasca, Illinois 60143

630/467-1300 • Fax: 630/467-1124industrialnetworking@putman.net

Editorial tEam Editor In Chief Joe Feeley Executive Editor Jim Montague Managing Editor Mike Bacidore Digital Managing Editor Katherine Bonfante Senior Technical Editor Walt Boyes Senior Technical Editor Dan Hebert Editorial Assistant Lori Goldberg

dEsign & ProduCtion tEam Art Director Derek Chamberlain

Publishing tEam Group Publisher/VP, Content Keith Larson Ad Traffic Supervisor Anetta Gauthier Director of Circulation Jack Jones Group Art Director Steve Herner

subsCriPtions888/644-1803

salEs tEamnortheastern and mid-atlantic regional manager

Dave Fisher • dfisher@putman.net24 Cannon Forge Dr., Foxboro, Massachusetts 02035

508/543-5172 • Fax: 508/543-3061

midwestern and southern regional managerGreg Zamin • gzamin@putman.net

555 W. Pierce Rd., Suite 301, Itasca, Illinois 60143630/467-1300 • Fax: 630/467-1124

Western regional managerLaura Martinez • lmartinez@putman.net

218 Virginia, Suite 4, El Segundo, California 90245310/607-0125 • Fax: 310/607-0168

inside sales manager Emily Rogier • erogier@putman.net

555 W. Pierce Rd., Suite 301, Itasca, Illinois 60143630/467-1300 • Fax: 630/467-1124

e-marketing account manager Jenny Fanning • jfanning@putman.net

555 W. Pierce Rd., Suite 301, Itasca, Illinois 60143630/467-1300 • Fax: 630/467-1124

rEPrintsFostereprints

Claudia Stachowiak • claudia@fostereprints.com866/879-9144 ext.121 • www.fostereprints.com

advErtisEr PagE no.AutomationDirect .................................................... 2

Beckhoff Automation .............................................. 6

GarrettCom ...............................................................23

Moxa Technologies .................................................. 4

N-Tron ........................................................................... 9

Omega Engineering ................................................ 3

ProSoft Technology................................................11

Sealevel Systems.....................................................19

Schweitzer Engineering Laboratories .............27

Transition Networks...............................................28

nEW on thE WEb

For a description of Siemens’ new Simatic ET 200pro IWLAN wireless I/O module, which is based on IEEE 802.11 WLAN standards and supports deterministic iPCF (industrial point coordination function), browse to www.IndustrialNetworking.net/siemens.

IN09Q3_24_25_Products.indd 25 7/16/09 11:47 AM

f i r s t b i t

John Rezabekjrezabek@ispcorp.com

industrial networking

Q3 • 200926

f i r s t b i tp a r i t y c h e c k

A while Ago, our instrument speciAlist made the rounds of remote multiplexor panels to check for power-supply failures. in recent years, we’ve been a little alarmed to find one of the two redundant dc power supplies failed. we unknowingly were limping along on a single power supply, at risk of losing an entire node of multiplexed i/o.

These measurements are “indicate only,” mostly thermocouples and rtDs, not essential to the

functioning of the plant. nonetheless, losing an entire bank would be unnerving for operators.

what’s a little ironic is that this power-supply health information is available through the multiplexor system’s standard diagnostics, over the same modbus 485 link through which we get the process data. if we just set up the serial interface to query a few more registers, we’d have access to a wealth of diagnostics—not only power-supply status, but individual i/o card statuses, communication status and more.

The same is true of a number of other devices connected through serial interfaces, including analyzers, flow meters and small plcs. why aren’t we making full use of the diagnostics we have?

one of the challenges is the time it takes to decode and test the diagnostics available. This data often is a bit string, so the developer or end user has to figure out which bits mean what and whether a zero is good or vice versa. testing sometimes can be a challenge. if you have to fail something, you risk a potentially wider malfunction. usually when i tell an operations supervisor, “nothing bad should happen, but there’s a chance you’ll lose all 120 temperature indicators in Area K,” the response is: “can you do this on someone else’s shift?”

especially when hardware is reliable, implementing diagnostics like these, which require a little effort, becomes a task akin to reading the manual—that is, no one bothers until something’s broken. But it only takes a few small victories to convince your boss that the effort needn’t repeatedly return to the back burner.

one of the common pieces of hardware that fall in the category of “reliable and therefore forgotten” is the ethernet switch. i have a pair of 3comm superstack switches—my system supplier doesn’t even recommend them anymore—that have been

cruising along bumplessly for years. But a sudden failure of one of these switches, or even a node becoming isolated, would be pretty troubling. i’m not even sure if i can get spare parts. why aren’t i pulling in some of its diagnostics, or at least viewing them directly on occasion? more modern industrial switches have support for modbus and opc, which might make it simpler for an end user to configure, display and trend some of the

switches’ more interesting statistics.A very rudimentary diagnostic is to try to

capture or derive a status for the points coming in over a serial link. our implementation has the unlucky feature of holding last value—flat-lining—on communications loss, like one would experience if both redundant power supplies failed. to implement status, we first have to choose a variable type that supports status and then either do an “AnD” of some selected diagnostic bits and set the point’s status accordingly or test if at least the “comm. Fail” state is flagged correctly by the serial interface device. if you already are living with a configuration that includes hundreds of such points, this could be a long effort. it’s much easier to implement when you’re deriving your templates early in the design phase. some systems support classes of modules, which can be a path for mass-editing of a class of module, such as serial modbus data points.

Another interesting diagnostic that end users could exploit more is the “Ao readback” variable of hArt valve positioners. This represents the actual valve position as seen by the positioner. to get it, you need a hArt-capable i/o card. patching it back from an asset-management system—using opc, for example—could be a little dicey, as the possibly long and variable latencies make the potential for stale data large. some hArt polling applications can take a long time—hours—to cycle through all the hArt devices.

By making full use of diagnostics we already have, we not only help our enterprise and the people who come after us, we encourage and push our supplier counterparts to provide us with diagnostics that are timely, meaningful and easily accessible.

John rezabek is a process control specialist at isp in lima, ohio.

when i tell

an operations

supervisor, “nothing

bad should

happen, but there’s

a chance you’ll

lose all 120

temperature

indicators in area k,”

the response

is: “can you do

this on someone

else’s shift?”

Diagnostics—Use What You Have

IN09Q3_26_ParityCheck.indd 26 7/16/09 11:49 AM

Improve Your Network Reliabilityat www.selinc.com/8in

Learn how to

Tough. Reliable. Safe.Convert and Switch Ethernet Links With the SEL-2725 Ethernet Switch

• Withstands harsh environments without dropping packets

• Improves safety and noise immunity with fiber optics

• Includes ten-year, worldwide warranty

www.selinc.cominfo@selinc.com+1.509.332.1890

Can Your Network Take This?

Electrostatic Shock (15 kV)Vibration (15 g Shock)

Heat (+85°C) / Cold (—40°C)

IndNet_2725_Aug09_A5.indd 1 7/16/2009 1:36:30 PMIN09Q3_FPA.indd 27 7/17/09 1:54 PM

C

M

Y

CM

MY

CY

CMY

K

FACE-THE-TRIAL-IN.7x10.pdf 1 6/25/2009 10:42:13 AM

IN09Q3_FPA.indd 28 7/15/09 11:05 AM