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Teledyne API - T100 UV Fluorescence SO2 Analyzer Principles of Operation
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amount. Second, the instantaneous concentration must exceed the average in the long
filter by a portion, or percentage, of the average in the long filter.
If necessary, these filter lengths of these two modes may be changed to any value
between 1 and 1000 samples. Long sample lengths provide better signal to noise
rejection, but poor response times. Conversely shorter filter lengths result in poor signal
to noise rejection, but quicker response times.
13.7.2. CALIBRATION - SLOPE AND OFFSET
Calibration of the analyzer is performed exclusively in software. During instrument
calibration (refer to Sections 9 and 10) the user enters expected values for zero and span
through the front panel touch-screen
control buttons and commands the instrument to
make readings of sample gases with known 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 control buttons 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=XX
X
SO2 =XXX.X
< TST TST > CAL SETUP
Figure 13-25: Calibration Slope and Offset
13.7.3. TEMPERATURE AND PRESSURE COMPENSATION (TPC) FEATURE
As explained in the principles of operation, changes in temperature can significantly
affect the amount of fluoresced UV light generated in the instruments sample chamber.
To negate this effect the T100 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 T100 software includes a feature
which allows the instrument to compensation of the SO
2
calculations based on changes
in ambient pressure.
06807C DCN6650