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VT1422A Command Reference 271Chapter 7
CALibration
Parameters
Comments • CAL:TARE also performs the equivalent of a *CAL? operation. This operation
uses the tare constants to set a DAC which will remove each channel offset as
"seen" by the module's A/D converter. As an example assume that the system
wiring to channel 0 generates a +0.1 volt offset with 0 volts (a short) applied at
the Unit Under Test (UUT). Before CAL:TARE the module would return a
reading of 0.1 volts for channel 0. After CAL:TARE (@100), the module will
return a reading of 0 volts with a short applied at the UUT and the system wiring
offset will be removed from all measurements of the signal to channel 0.
• The CAL:TARE command may be issued to several VT1422As to be later
completed with a matching CAL:TARE? query sent to each instrument. Note if
the DIAG:CAL:TARE:OTD:MODE is set to "1" then the CAL:TARE command
will not return until the calibration is complete.
• Set Amplifier/Filter SCP gain before CAL:TARE. For best accuracy, choose the
gain that will be used during measurements. If the range or gain setup is later
changed, be sure to perform another *CAL?.
• If Open Transducer Detect (OTD) is enabled when CAL:TARE is executed,
the module will disable OTD, wait 1 minute to allow channels to settle, perform
the calibration and then re-enable OTD. If OTD is turned off by the program
before executing CAL:TARE, the application should also wait one minute for
settling. If the DIAG:CAL:TARE:OTD:MODE is set to "1", the OTD will
remain enabled throughout the TARE calibration. This allows the voltage
generated by the OTD current to also be removed by the TARE cal.
• The maximum voltage that CAL:TARE can compensate for is dependent on the
range chosen and SCP gain setting. The following table lists these values.
• Channel offsets are compensated by the CAL:TARE command even when not
stored in the Flash Memory. There is no need to use the CAL:STORE TARE
command for channels which are re-calibrated frequently.
Parameter
Name
Parameter
Type
Range of
Values
Default
Units
ch_list channel list (string) 100 - 15731 none
Maximum CAL:TARE Offsets
A/D range
± V F.Scale
Offset V
Gain x1
Offset V
Gain x8
Offset V
Gain x16
Offset V
Gain x64
16
4
1
0.25
0.0625
3.2213
0.82101
0.23061
0.07581
0.03792
0.40104
0.10101
0.02721
0.00786
0.00312
0.20009
0.05007
0.01317
0.00349
0.00112
0.04970
0.01220
0.00297
0.00055
n/a