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Model GFC7000E Instruction Manual Operating Instructions
04584 Rev A1 78
6.9.6. Dark Calibration Test
The dark calibration test interrupts the signal path between the IR photo-detector and the
remainder of the sync/demod board circuitry. This allows the instrument to compensate for any
voltage levels inherent in the sync/demod circuitry that might effect the calculation of CO
2
concentration. Performing this calibration returns two offset voltages, One for CO
2
MEAS and on
for CO
2
REF that are automatically added to the CPU’s calculation routine. The two offset voltages
from the last calibration procedure may be reviewed by the user via the front panel display.
To activate the dark calibration procedure or review the results of a previous calibration, press:
SAMPLE RANGE = 500.000 PPM CO2 =X.XXX
< TST TST > CAL SETUP
SAMPLE
ENTER SETUP PASS : 818
8 1 8 ENTR EXIT
SETUP X.X PRIMARY SETUP MENU
CFG DAS RNGE PASS CLK MORE EXIT
SETUP X.X SECONDARY SETUP MENU
COMM VARS DIAG ALRM EXIT
Calibration runs automatically
Electric offset for Measurement signal
Electric offset for Reference signal
DIAG SIGNAL I / O
NEXT ENTR EXIT
Repeat Pressing
NEXT
until . . .
DIAG DARK REF DARK OFFSET: 0.0 mV
EXIT
DIAG DARK MEAS DARK OFFSET: 0.0 mV
EXIT
DIAG DARK DARK CAL 1% COMPLETE
EXIT
DIAG DARK DARK CALIBRATION ABORTED
EXIT
Display
tracks %
complete
DIAG DARK CALIBRATION
PREV NEXT ENTR EXIT
Exit returns
to the
previous menu
DIAG DARK CO DARK CALIBRATION
VIEW CAL EXIT
6.9.7. Pressure Calibration
A sensor at the exit of the sample chamber continuously measures the pressure of the sample
gas. This data is used to compensate the final CO
2
concentration calculation for changes in
atmospheric pressure and is stored in the CPU’s memory as the test function PRES (also viewable
via the front panel).
NOTE