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Teledyne API M100E Analyzer Operation Manual Theory Of Operation
253
11.7.2. CALIBRATION - SLOPE AND OFFSET
Calibration of the analyzer is performed exclusively in software. During instrument calibration (refer to Chapters 8
and 9) the user enters expected values for zero and span through t
he front panel keypad and commands the
instrument to make readings of sample gases with know concentrations of SO
2
. The readings taken are
adjusted, linearized, and compared to the expected values as input. With this information the software computes
values for instrument both slope and offset and stores these values in memory for use in calculating the SO
2
concentration of the sample gas.
Instrument slope and offset values recorded during the last calibration can be viewed by pressing the following
keystroke sequence
SAMPLE RANGE = 500.000 PPB SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE TIME = HH:MM:SS SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE PMT TEMP=0.0C SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE BOX TEMP=0.0C SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE RCELL TEMP=0.0C SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE HVPS 553 VOLTS SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE OFFSET=XX.X MV SO2 =XXX.X
< TST TST > CAL SETUP
SAMPLE SLOPE=XXX SO2 =XXX.X
< TST TST > CAL SETUP
Figure 11-24: Calibration Slope and Offset
11.7.3. TEMPERATURE AND PRESSURE COMPENSATION (TPC)
FEATURE
As explained in the theory of operations (refer to Chapter 11) changes in temperature can significantly affect the
amount of fluoresced UV light generated in the instruments sample chamber. To negate this effect the M100E
maintains the sample gas at a stable, raised temperature.
Pressure changes can also have a noticeable, if more subtle, effect on the SO
2
concentration calculation. To
account for this, the M100E software includes a feature which allows the instrument to compensation of the SO
2
calculations based on changes in ambient pressure.
When the TPC feature is enabled, the analyzer’s SO
2
concentration divided by a factor call PRESSCO which is
based on the difference between the ambient pressure of the sample gas normalized to standard atmospheric
pressure (Equation 11-6). As ambient pressure in
cr
eases, the compensated SO
2
concentration is decreased.
04515F DCN6048