Teledyne 100AH instruction manual 10.3.2.1 ADC/DAC Calibration Procedure, 10-35

Teledyne API Model 100AH SO2 Analyzer Instruction Manual, 02417, Rev. D

10.3.2.1 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 to the 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 10.1.6.

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 M100AH display will read "ADJUST ZERO A/D= XX.X mV", where XX.X mV is the target voltage that 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 M100AH 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 M100AH 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 that 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.

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