User's Manual

Teledyne API Model 401 O

Photometric Calibrator Instruction Manual, 01124, Rev. J2

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.

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