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SCXI-1125 Calibration Procedure 8 ni.com
• filterMode—1
• cutoffFrequency—10,000
9. Connect the calibrator to the analog input you want to adjust. Refer
to Figure 1 to determine the pins on the 96-pin front connector that
correspond to the positive and negative inputs of the specified channel.
For example, the positive input for channel 0 is pin A32, which is
labeled CH0+. The negative input for channel 0 is pin C32, which
is labeled CH0–. If you are using an SCXI-1320 terminal block
connected to the SCXI-1125, connect the calibrator to the CH0+
and CH0– inputs.
10. Connect the DMM to the positive output on pin 3 (MCH0+) and
negative output on pin 4 (MCH0–) on the rear panel connector.
Figure 2 shows the 50-pin rear panel connector.
Tip
For easy access to individual pins, use a screw terminal adapter connected to a
50-pin terminal block.
11. Set the calibrator voltage to the positive test point value in Table 1.
12. Read the voltage from the DMM. Record the actual DMM reading,
which is output1, and the calibrator output voltage, which is volt1,for
later use.
13. Set the calibrator to the negative test point value for the same gain.
Skip any input limits that are specified as 0.0 V. You need only upper
and lower limits for adjustment.
14. Read the voltage from the DMM. Record the actual DMM reading,
output2, and the calibrator output voltage, voltage2.
You now have two pairs of data points, (volt1, output1) and (volt2,
output2), where volt is the calibrator reading and output is the DMM
reading.
15. Convert the DMM voltage readings (output1 and output2)tobinary
readings (binary1 and binary2) by using one of the following
equations:
For example, using a 12-bit product such as a PCI-MIO-16E-1 and
obtaining a DMM reading of –9.9 V, you would have the following
results:
binary reading =(–9.9/20) × 2
12
= –2027.52
binary reading for 12-bit E Series products (binary)
output
20
-----------------
2
12
×=
binary reading for 16-bit E Series products (binary)
output
20
-----------------
2
16
×=