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Theory of Operation T400 Ozone Analyzer Operator’s Manual
304
Two conditions must be simultaneously met to switch to the short filter. First, the
instantaneous concentration must exceed the average in the long filter by a fixed
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.
13.5.2. CALIBRATION - SLOPE AND OFFSET
Calibration of the analyzer is performed exclusively in software. During instrument
calibration, (see Sections 9 and 10) the user enters expected values for zero and span via
the front panel touchscreen and comman
ds the instrument to make readings of calibrated
sample gases for both levels. The readings taken are adjusted, linearized and compared
to the expected values. With this information, the software computes values for
instrument slope and offset and stores these values in memory for use in calculating the
O
3
concentration of the sample gas.
The instrument slope and offset values recorded during the last calibration can be
viewed by pressing the following control button sequence:
SAMPLE RANGE = 500.0 PPB O3 =XXX.X
< TST
TST > CAL SETUP
SAMPLE
TIME = 16:23:34
O3 =XXX.X
< TST
TST > CAL SETUP
SAMPLE
OFFSET = 0.000
O3 =XXX.X
< TST
TST > CAL SETUP
SAMPLE
SLOPE = 1.000
O3 =XXX.X
< TST
TST > CAL SETUP
06870C DCN6332