NI 9219 Calibration Procedure
12
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7.
Disconnect the DMM from the resistor to ensure that the terminals on the DMM do not interfere
with the resistor while the NI 9219 makes measurements.
8.
Clear the task.
9.
Create an AI resistance channel on the NI 9219. Configure the channel according to Table 10.
10. Acquire 20 2-wire resistance readings with the NI 9219. Record the average of the readings as
channel
.
11. Perform the following calculation using the recorded
ref
and
channel
values.
12. Compare the calculation result to the Upper Limit and Lower Limit values in Table 11.
13. Clear the acquisition.
14. Disconnect the resistor from the device.
15. Repeat steps 1 through 14 for all test points and channels on the NI 9219. NI recommends that you
verify the values for all the iterations listed in Table 11 for each channel, but you can save time by
verifying only the values and channels used in your application.
Quarter-Bridge Accuracy Verification
Complete the following steps to verify the quarter-bridge accuracy of an NI 9219.
1.
Connect the NI 9219 to the resistor and the DMM as shown in Figure 6. Observe the following
conditions when connecting the equipment to the NI 9219.
•
Connect the leads of the DMM as close as possible to the terminals on the NI 9219 to ensure
that the DMM reference measurements include the same lead wire resistance as the NI 9219
quarter-bridge measurement.
•
Secure the spring-terminal connectors to the NI 9219 using the captive screws.
Table 10.
NI 9219 Configuration for 2-Wire Resistance Accuracy Verification
Measurement Type
Min (
)
Max (
)
Excitation
Source
Excitation
Value
ADC Timing
Mode
Sample
Timing Type
2-Wire Resistance 1 k
0
1000
Internal
0.0005
High
Resolution
On Demand
2-Wire Resistance 10 k
10000
Table 11.
NI 9219 Verification Test Limits for 2-Wire Resistance Accuracy
Mode
Range
Test Point
1–Year Limits
Min (
)
Max (
k
)
Location
Value
Lower Limit (
)
Upper Limit (
)
2-Wire
Resistance
1 k
0
1.05
Max
845
±1%
–1.15
1.15
Min
20
±5%
–0.50
0.50
2-Wire
Resistance
10 k
0
10.5
Max
8450
±1%
–7.20
7.20
Min
20
±5%
–0.64
0.64
Accuracy
channel
ref
–
=
