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NI 9218 Calibration Procedure
c.
Call and configure the DAQmx Setup 9218 Calibration function according to
Table 30.
d.
Configure DMM1 for a voltage measurement in the 10 V range.
e.
Enable autozero on DMM1.
f.
Configure DMM2 for a voltage measurement in the 100 mV range.
g.
Enable autozero on DMM2.
h.
Call the DAQmx Get 9218 Calibration Adjustment Points function to obtain an array
of recommended calibration points for the NI 9218. The adjustment points can be
achieved by observing the following conditions.
•
The max test point is achieved by following the diagram in Figure 6.
•
The mid test point is achieved by following the diagram in Figure 7.
•
The min test point is achieved by following the diagram in Figure 8.
i.
Acquire voltage measurements with both DMMs. Perform the following calculation
using the two DMM measurements.
Note
Perform the DMM measurements simultaneously in order to reduce error
from drift in the resistors.
j.
Call and configure the DAQmx Adjust 9218 Calibration function according to
Table 31.
Note
The NI 9218 acquisition starts each time the adjustment function is called.
k.
Repeat steps d through k for every value in the array.
l.
Close and commit the calibration session.
4.
Repeat steps 3c through 3l for each channel on the NI 9218.
5.
Disconnect the DMMs and the resistors from the NI 9218.
Table 30.
Setup Configuration for Bridge Accuracy Adjustment
Min (V/V)
Max (V/V)
Physical Channels
Measurement Type
-0.022
0.022
cDAQMod8/ai
x
Bridge
Table 31.
Adjustment Configuration
Physical Channel
Reference Value
cDAQMod8/AI
x
Ratio
ref
Ratio
ref
V
DMM
2
V
DMM
1
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