Test V-7: Shunt Cal Resistor Port - VXI VT1422A User Manual

Test V-7: Shunt Cal
Resistor Port
Description
Procedure
474 VT1529A/B Verification & Calibration
This test verifies the operation of the switches associated with the front panel
Shunt Cal Resistor port. The operation of these switches can be verified by
observing the changes in the bridge output voltage when external shunt
calibration is disabled and enabled.
A 1 kΩ external shunt resistor is connected to the Shunt Cal Resistor port
and the Dummy Load is attached. The 350 Ω bridge completion resistor path
is configured. With the external shunt disabled, the bridge output voltage
should be:
V = V
sense
With V
excitation
With the external shunt enabled, the bridge output voltage should be:
V = V
sense
Where R equals the parallel combination of the 350 Ω resistor and the 1 kΩ
external shunt or 259.26 Ω. Again, with V
value of V
sense
Note that the actual measurements will vary based on the actual resistor
values in the dummy load, so these values should be considered approximate
when running this test.
Setup
The VT1529A/B must be connected to the VT1422A through the VT1539A
SCP. The Dummy Load must be connected to the channel(s) being tested.
The Voltage Source must be connected to the appropriate channel bank
terminals of the Bridge Excitation input on the VT1529A/B.
The signal path through the VT1529A/B is highlighted in Figure C-5.
If necessary, send the *CAL? query to the VT1422A (required if more than
8 hours has elapsed since the last *CAL? command). The expected return
value is "+0".
Set the Voltage Source to 5.000 V.
Configure the VT1529A/B for 350 Ω quarter-bridge operation using the
SENS:FUNC:STR:Q350 (@<ch_list>) command. Disable shunt
calibration by sending the OUTP:SHUNt OFF,(@<ch_list>) command.
Send the MEAS:VOLT:UNStrained? (@<ch_list>) query to the VT1422A.
The expected return value is ~0.301 V on each channel. Now, configure
for external shunt using OUTP:SHUNt:SOURce EXTernal,(@<ch_list>).
For each channel (each must be tested separately), enable external shunt
calibration by sending the OUTP:SHUNt ON,(@<channel>) command.
Note: this turns off the shunt on the previous channel.
Send the MEAS:VOLT:UNStrained? (@<channel>) query to the
VT1422A. The expected return value is ~0.315 V on each channel.
* (10 / (10 + 7.5 + .350) - 0.5)
excitation
= 5.0 V, the expected value of V
* (10 / (10 + 7.5 + R) - 0.5)
excitation
is 0.315433 V.
is 0.301120 V.
sense
= 5.0 V, the expected
EXCITATION
Appendix C