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9.2 A/D - D/A Calibration procedure
Due to the stability of modern electronics, this procedure should not have to be
performed more than once a year or whenever a major sub-assembly is exchanged or
whenever analog output voltage range is changed .
To calibrate the ADC, do the following:
1. Press SETUP-MORE-DIAG.
2. Enter Diagnostic password and press NEXT until D/A CALIBRATION
appears in the display and press ENTR.
3. Press ADC to perform the A/D Cal.
4. The M300 display will read "ADJUST ZERO:A/D=xx.x MV.” Put the probe
of a voltmeter between TP3(AGND) and TP9(DAC #0) on the top of the V/F
card (See Drawing 00514, Appendix C)
5. The value displayed by the voltmeter should be close(+/- 20 mV) to the value
on the M300 display. If they are not close then the V/F card has probably
been configured improperly.
6. Adjust the Zero pot(R27) on the V/F card until the value on the M300 display
matches the value on the voltmeter to within +/- 2 mV. Note that when
adjusting R27, the value on the M300 display will change, the value on the
voltmeter will remain constant.
7. Press ENTR.
8. The M300 display will now read "ADJUST GAIN:A/D=xx.x MV.”
9. Adjust the Span pot(R31) on the V/F card until the value on the M300 display
matches the value on the voltmeter to within +/- 2 mV.
10. Press ENTR.
11. The ADC is now calibrated and the M300 will automatically calibrate all the
DAC’s. This process takes only a few seconds
12. Press EXIT 4 times to return to the sample menu.
9.3 Dark current signal adjust procedure
The detector dark current changes little as the detector ages. Therefore this procedure
should not need to be performed more than once per year or whenever a major
sub-assembly is changed To calibrate the dark current signal, press
SETUP-MORE-DIAG-DARK-CAL and the analyzer will automatically do the
following:
1. Disconnect the detector output from the processing electronics
2. Wait 2 minutes for electronics to stabilize at the dark value
3. Average CO MEAS and CO REF reading for 1 minute
4. Reconnect the detector output to the processing electronics to the
processing electronics.
The average CO MEAS and CO REF dark reading are stored as offsets which are
subtracted from all future CO detector readings.
P/N 02163G1 Teledyne API Model 300 CO Analyzer Instruction Manual - Page 79