A/D - D/A Calibration Procedure - Teledyne 401 Instruction Manual

Teledyne API Model 401 O

8.2 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-MISC-D/A-CAL.
2. The M401 display will read "DAC #0: 60 mV", where 60 mV * is the target voltage which
should be coming out the DAC (it should be 60 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
E), then press the up/down buttons on the M400 front panel until the voltmeter displays the
target voltage (60 mV on the 5 V range). Note that the value on the M401 display will not
change. When the voltmeter shows the same value ( ± 3 mV) as the M401 display, press
ENTR.
* The reading will be close to 60 mV if the analyzer is setup for the 5 V range, 120 mV for
the 10 V range, etc. DAC #0 is the recorder output, DAC #1 is the DAS output, and DAC #3
is the test output.
3. The M401 display will now show a new voltage in the same format as above. This voltage
will be 90% of the full scale DAC output range (4500 mV on the 5 V range). As before, press
the up/down buttons on the M401 front panel until the voltmeter displays the same ( ± 3 mV)
reading as the M400 display, then press ENTR. The first DAC is now calibrated and will be
used as a voltage reference for calibrating the ADC.
4. The M401 display will now read ZR:60 = 60 ± 3 mV, where 60 mV is the voltage being
output from the DAC as input to the ADC, and 60 ± 3 mV is the voltage as read from the
ADC. The two values should be the same (60 = 60). If they are not, adjust the zero pot (R27)
on the V/F card (as indicated by ZR on the display) until the two values are the same, then
press ENTR.
5. The M401 display will now read GN:4500=4500 ± where 4500 is the voltage being output
from the DAC as input to the ADC, and 4500 ± 3 is the voltage as read from the ADC. The
two values should be the same. If they are not, adjust the gain pot (R31) on the V/F card (as
indicated by GN on the display) until the two values are the same (4500 = 4500 ± 3 mV),
then press ENTR. The ADC is now calibrated and M401 will automatically calibrate all the
DAC's. The display will show the percent completion as the analyzer goes through the
procedure.
Photometric Calibrator Instruction Manual, 01124, Rev. J1
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