NI 9235/9236 Calibration Procedure
12
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15. Compare the compensated result for each value to the Upper Limit
(V/V) and Lower Limit (V/V) values in Table 5 for the NI 9235 and
Table 6 for the NI 9236. If the result is between these values, the device
passes the test.
Note
You can analyze data in V/V form or convert it to strain using the standard
quarter-bridge equation:
where
V
r
is the compensated reading from the NI 9235/9236 and
GF
is a gage factor of 2.
16. Repeat steps 3 through 15 for all channels.
17. Set the calibrator to standby mode (STBY).
18. Disconnect the calibrator from the device.
Shunt Calibration Accuracy Verification
Complete the following steps to test the shunt calibration accuracy of the
device:
1.
Using the DMM and 4-wire resistance measurement connections,
measure the resistance of the wire to be connected between the
calibrator LO terminal and the module RC terminal, and record the
result for later use. You must do this because this connection to the
module creates a lead wire desensitization error. This results in module
readings that are systematically lower than the true shunt calibration
output. Knowing the actual resistance value, however, allows for
compensation of this effect.
2.
Set the calibrator output for two-wire compensation (COMP 2-wire).
This automatically compensates for the lead wire resistance between
the HI terminal of the calibrator and the EXC terminal of the module.
3.
Connect the calibrator to the channel you want to verify, as explained
in the
Connecting the Calibrator to the Module
section.
4.
Set the calibrator resistance output to 120
Ω
for the NI 9235 or 350
Ω
for the NI 9236.
strain
ε
( )
4
–
V
r
×
GF
1
2
V
r
×
(
)
+
(
)
-------------------------------------------
=