Teledyne 6200A - Sulfides analyzer - Manual (Page 181)

TAI Model 6200A SO
2
Analyzer Operator Manual, 02164, Rev. G
9.3.3.1 ADC/DAC 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 4-20 mA current option output, proceed second part of
the procedure for the calibration of 4-20 mA current output. After this procedure is completed, a
Factory Calibration Procedure should be performed per Section 9.1.6.
To calibrate the DAC's on the V/F board, do the following:
1. Press SETUP-MORE-DIAG-ENTR, then scroll down to the D/A CALIBRATION diagnostic
mode, then press ENTR to start the calibration procedure.
Press CFG-SET-VOLT-ENTR to define Voltage output of the corresponding Analog Output
Channel. If necessary a recorder offset can be introduced into the analog output voltages. It is
intended for recorders that cannot show slightly negative readings. It can also be used to bias
the input to a datalogger to offset small external ground loop voltages that are sometimes
present in monitoring systems. The recorder offset will bias both the recorder and DAS
analog outputs. Enter offset value in mV as needed and press ENTR-EXIT.
2. Press ADC to start the calibration. The 6200A display will read "ADJUST ZERO A/D=
XX.X mV", where XX.X mV is the target voltage which should be coming out the DAC # 0.
Put the probe of a voltmeter (recommend to use 4 1/2 digits meter) on the recorder output
terminals 1 and 2 on the 6200A rear panel. The value displayed on the front panel and the
voltmeter reading should be the same (
± 3 mV). If they are not, adjust the zero pot (R27) on
the V/F board until the two values are the same ( ± 1 mV). Note that the voltmeter reading
does not change while adjusting the zero pot (R27). When the voltmeter shows the same
value(± 1 mV) as the value displayed on the front panel, press ENTR.
DAC #0 is terminals 1 and 2 of the recorder output.
3. The 6200A display will now show a new voltage in the same format as above. This voltage
will be about 90% of the full scale DAC output range. Now the value displayed on the front
panel and the voltmeter reading should be same (
± 3 mV). If they are not, adjust the gain pot
(R31) on the V/F board until the two values are the same ( ± 3 mV). Press ENTR. The DAC
#0 is now calibrated and will be used as a voltage reference for calibrating the ADC.
4. Next, the analyzer goes through a procedure which calibrates the other 3 DAC's. When
completed press EXIT to return to upper level menus.
Next setup is recommended to verify the quality of the ADC/DAC calibration.
5. Pressing SETUP-MORE-DIAG-ENTR-NEXT, and select ANALOG OUTPUT. Verify the
quality of ADC/DAC calibration by measuring the test channel output voltage. The signal
consists of a scrolling 0%, 20%, 40%, 60%, 80%, 100% of the analog output value. The
scrolling may be stopped by pressing the key underneath the % display to hold that value and
will display within the square bracket ( [%] ). Press key once again to continue scrolling or press
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