Laser Diode Gas Sensors - Swissphotonics :: Home
Transcript of Laser Diode Gas Sensors - Swissphotonics :: Home
Laser Diode Gas SensorsPhotonic SensorsSwiss Laser Net Workshop Biel 17.09.09
Thomas Hessler
Overview
Leister and ist photonic activities
TDLS detection principle
TDLS product plattform
Applications
PLASTIC WELDING PROCESS HEAT LASERSYSTEMS MICROSYSTEMS
LEISTER Process Technologies
LEISTER Corporate
Production,Logistics
Corporate HeadquarterMarketing & Sales,Administration,Corporate R&D
Axetris,Production
Sarnen, CHKägiswil, CHKägiswil, CH
Corporate Sites
Photonic Sensor Activities at Axetris
Laser Gas SensorsTunable Diode Laser Gas Sensors
IR SourcesBroad band thermal IR emitters for NDIR gas sensors
Micro-OpticsRefractives and diffractives for opticalsensors
p. 6
Reference
GasVolume
Detector
IR Source
Technology - TDLS Measurement Principle
Laser diode scan acrosssingle gas absorption line.
Laser Scan
Laser line
Gas absorption lines
λ
A
λ
A
GasVolume
Laser
Laser signal information:Laser intensity & wavelengthvary linearly with drive current
Gas absorption signal:The detector sees less intensityas the laser hits the gas line
Optical system & reference information: On modulation frequency f
Gas concentration signal:On modulation frequency 2f
I
I
t
t
No gas
With gas
f
2f
λ
λ
Intrinsic reference channelHigh linearity
Laser signal information
Laser Scan
Gasabsorption information
λ
A
Technology - TDLS Measurement Principle
Technology – 1st or 2nd Order
Optical and optoelectronic components (laser & detector) increase significantly in price with wavelength (if available)=> work at 1st or 2nd overtone
Abs
orpt
ion
Wavelength (µm)
4.262.041.57
FundamentalAbsorption Band Envelope1st
Overtone
2nd
Overtone
CO2
1,57 1,571 1,572 1,573 1,574 1,575
COCO
2
Abs
orpt
ion
(a.U
.)
Wavelength
TDLS - Selectivity
TDLS is a high resolutionmeasurementSuperposed bands can beresolved for each gas: Results in high selectivityExample CO2/CO: Envelopes overlap, single absorption lines do not
TDLS - Good for small molecules
TDLS can measure gases with resolved rotation & vibration bands, i.e. gases with small molecules.E.g. alkanes: Ok for CH4, C2H6, but not for longer chains
Electronics
Laser Diode
Mirror
Photo Diode Gas Volume
Technology - Laser Gas Monitor
Sharp laser linehigh selectivity
Intrinsic reference channelhigh, long term stability, calibration-freecontinuous status monitoring
Optical technologycontactless & hot gas measurement
Business Focus
Laser gas detectionPresent Focus on NH3, CH4, CO2, O2Flow through and diffusive set-upsSelf-contained OEM modules, sub-mounts
Applications inProcess control & environmental monitoringIndustrial safety Climate & air conditioningMedical technology
IR Microsystems provides:Self-contained measurementsystem with integrated optics(probe or flow-cell)Digital or analog data output
Customer provides:Input Power (10-30 V)Conditioned/filtered gasPurge gas (where necessary)
Measurementinterface to customer:
TDLS Gas Monitor Set-up
Diffusive: LGD P50 Single point
Flow: LGD F200 (H) Ambient / heated
Technology (Flow) - LGD F 200 (H)
Flow-through cellOptional heating up to 190°CModular design
System Specifications
below detection limitDriftdepending on gas & applic. ppm- or %-rangesMeasurement rangedepending on gas & applic.modular, different path lengthsMeasurement cell layout
ambient, optional up to 190°CMeas. temp. flow-throughflow-throughLGD F200H layout
800 ppm130 ppmOxygenO2
30 ppm5 ppmCarbon DioxideCO2
3 ppm0.5 ppmMethaneCH4
2 ppm0.3 ppmAmmoniaNH3
Peak-to-peak noiseat T: -40°C to +65°C
Precisionat T constantMain Target Gases
LGD F 200 (H) - Specifications
~Compact multigas
~~Acquisition cost
TDLS
~
E-Chem
Calibration-free~~High Stability~~High Selectivity
~Overload damage or ageing
Fast Recovery time
Rugged~~Low cost-over-time
Non-contact measurementCont. Sensor status monitoring
Paramag.NDIR
Characteristics
Gas Sensing Technologies
Selected ApplicationsNH3
SCR / Emission Control
Safety / Refrigeration
Livestock Climate Control
CH4
Environmental Monitoring / Landfill
SCR system monitoring, combustion processes inpower plants, powerstations, diesel engine development
Need to measure NH3 hot (190°C) to 1ppm(acid dew point, water)
LGD F200 H offers real time emission controlwith non-contact measurement in heated sample cell
0.3 ppm2 ppm
Precision at T = const.:Peak-Peak Noise -40°C – 65°C:
SelectivityNon-contact
Main application specific USP
SCR Process Monitoring
Emission Control
0
1
2
3
4
5
6
7
8
9
10
11
12
500 1000 1500 2000 2500
Time [s]
Set 7 ppm
Set 8 ppm
Set 9ppm
Set 10 ppm
Set 0 ppm
Set 2 ppm
Set 6 ppm
Set 5 ppm
LGD F200 NH3 - measurements
resolution
LGD F200 NH3 - measurements
linearity reproducibility
LGD F200 NH3 - measurements
Workplace and site safety monitoring: 1-100 ppmCurrent sensors:
Life time ~ 12 months, 6-months calibration cycleHigh cost for end-userNo sensor status monitoringCross sensitivities / false alarms
microLGD offers better performance at lowercost-over-time
Plant & personnel safety monitoring
0.3 ppm2 ppm
Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:
Selectivity ReliabilityCost-over-time
Main application specific USP
Safety / Refrigeration
Monitor NH3 to improve health and growth of livestockScrubb NH3 out of exhaust air for environmental protection
Well-suited sensors are not available today
Current sensors:Life time shortened to days by NH3 backgroundCross sensitivities
microLGD enables livestock applications
Ventilation Control & Ammonia Scrubbing
0.3 ppm2 ppm
Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:
Life-timeCost-over-time
Main application specific USP
Livestock Climate Control
0.3 ppm3 ppm
Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:
SelectiveHigh dynam. range
Main application specific USP
Landfill / waste water gas monitoring
Monitoring of waste water for CH4emission; landfill de-gasing (safety)
LGD F200 offers real time,monitoring with high dynamic range
Selective measurement of methane
0
2
4
6
8
10
12
14
0 500 1000 1500C
H4 [p
pm]
Time [s]
5 ppm
6 ppm6.9 ppm
7.9 ppm
10 ppm
3.9 ppm
2 ppm
0 ppm
Environmental Monitoring
Summary
The optical, non-contact measurement principle and the intrinsic reference channel and the high selectivity offer significant benefit in a wide range of applications. TDLS moves from high end to upper medium end applications, component cost hinder further penetration into mainstream applications.Leister offers self-contained laser gas monitoring systems to OEMs to use the benefits of this technology in their field of activity.
Thank you for your attention!