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National Instruments Corporation
15
NI 446X Calibration Procedure
10. Average all the values in the array returned from the acquisition. The
average is the resulting offset for AI 0 at –20 dB device gain setting.
Compare this value to the limits in Table 2.
11. Repeat steps 2 through 10 for each different gain value that is set in
step 4, using the device gain values in Table 2.
12. Repeat steps 1 through 11 for all remaining analog input channels of
the device. Replace
ai0
with the appropriate channel name in function
call parameters
physicalChannel
and
channel
.
Verifying AI Gain Accuracy
Complete the following steps to verify AI gain accuracy:
1.
Connect the output of the calibrator to the analog input channel 0 of the
device.
2.
Output 9.0 VDC using the calibrator.
3.
If you use C function calls, create a task using the following function.
If you use LabVIEW, skip this step. The task is created in step 4 in
LabVIEW.
You use the object
myTaskHandle
in all subsequent NI-DAQmx
function calls.
Table 2.
AI Offset Limits
Device Gain
Device Input Offset
Min (mV)
Max (mV)
–20
–7.0
7.0
–10
–5.0
5.0
0
– 0.7
0.7
10
– 0.5
0.5
20
– 0.2
0.2
30
– 0.1
0.1
NI-DAQmx Function Call
LabVIEW Block Diagram
Call
DAQmxCreateTask
with the following parameter:
taskHandle
:
mytaskHandleReturnValue
LabVIEW does not require this step.