Correlation Measurement for Process Quality Analysis · Correlation Measurements for Process...
Transcript of Correlation Measurement for Process Quality Analysis · Correlation Measurements for Process...
Correlation Measurements for Process Quality Analysis
ApplicationsDetection of Periodicities
Prediction of Signals in ‘Noise’
Measurement of Time Delays
Location of Disturbance Sources
DepartmentsResearch and Development
Production Testing
Engineering Test
Quality Assurance
Description
Paper is the culmination of a long series of process
stages that are all prone to variations due to raw
materials, time and operator set up. While there are
several properties that are used to define the quality
of paper, its weight (basis weight) is the most
fundamental and reducing the variation in basis
weight has been pursued with the greatest vigor of
any single property. Low frequency, machine
direction basis weight variation is usually traceable to
problems upstream in the machine, in the stock
approach system. The problems generally stem from
either pulsation in the stock system or from an
inability to maintain a uniform consistency in the
stock.
Problem
Troubleshooting an MD weight variation requires the
ability to simultaneously acquire and analyze a
variety of signals such as on-machine basis weight,
thin stock consistency, stock approach system
pressure (at several locations), vibration and drive
motor parameters such as speed, etc. A complex array
of time and frequency domain measurements is then
required to properly characterize and solve the
problem. Users often attempt to perform only
frequency domain measurements to analyze the
nature and sources of variation in the system with
coherence function measurements to provide a
measure of causality between different signals.
However, in most process environments, it is essential
that a degree of similarity as well as the direction of
propagation along with lag time is available when
comparing different signals. Correlation
measurements are the only answer to problems like
these.
Solution
The SignalCalc Mobilyzer equipped with 8 to 16
channels is the ideal platform for fast and flexible
in-mill data acquisition, analysis and reporting. The
Application Note: DP-AN05-001
Poor tooth contact
Windows based Dynamic Signal Analyzer software
offers Correlation measurements as a standard
feature. Users can view the unfiltered and filtered
time domain data for all channels and analyze the
average cross correlation measurements between
the various signals. All this can be accomplished
while recording raw data simultaneously at either
the measurement sample rate or a different sample
rate, specified by the user.
Implementation
The measurements begin with the setup of
multiple sensors coupled to the Abacus front-end.
The high input impedance, differential inputs of the
acquisition module allow direct connection to the
on-machine basis weight scanner that is generally
operated in single-point mode for the correlation
measurements. Pressure sensors on both sides of
the pumps, screens, de-aeration devices and the
headbox along with thin and thick stock
consistency meters provide the other essential
measurements for the analysis. By adjusting the
length of time blocks and with the use of special
filters that are user defined, the magnitude and
source of the basis weight variations may be
identified.
Key System Features
Intuitive and Flexible Graphical User InterfaceEU Offset Calculation for Signals with DC contentBi-Directional, Normalized Cross CorrelationRemoval of Mean Value before CorrelationUser Definable Low Pass, High Pass, Band Pass and Band Reject FiltersUnlimited Display LayoutsThroughput Recording to Local Bus Disk
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Real
Reel BW Scanner, Hdbx TS
R1, 7Peak #1 X: -29.3457 Y: 0.2959
20 40 60 80 100 120 140 2.260
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psi
Hdbx TS
PkPk: 0.0852Mean: 2.3071StdDev: 0.0142
X7 X: 0 Y: 2.3001X7 X: 150.0000 Y: 2.2885 dX: 150.0000 dY: 0.0115
40 60 80 100 120 140 160 51.500
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Reel BW Scanner
PkPk: 2.3513Mean: 53.3409StdDev: 0.4172
X1 X: 29.3457 Y: 53.3406X1 X: 179.3457 Y: 52.9272 dX: 150.0000 dY: 0.4135
Hardware
DP700-30-A1Network Peripheral
DP700-30-16CDSPCentric Signal ProcessingHardware – 16 Channels
DP730-23Throughput to Disk and PlaybackAnalysis
Part Number and Description Qty
DP730-10Windows Based Dynamic Signal Analyzer Software
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Software