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National Instruments Corporation
11
SCXI-1141/1142/1143 Calibration Procedure
6.
Connect the calibrator to the appropriate analog input channel, starting
with channel 0. Refer to Table 7 to determine the pins on the 96-pin
front connector that correspond to the positive and negative inputs of
the specified channel. If you are using an SCXI-1304 connected to the
SCXI-1141/1142/1143, connect the calibrator to the AI 0 + and AI 0 –
inputs and verify that the SCXI-1304 is set to DC coupling.
7.
Connect the DMM to the positive output on pin 3 (AI 0 +) and the
negative output on pin 4 (AI 0 –) on the rear panel connector,
illustrated in Table 8.
Tip
For easy access to individual pins, use a TBX 50-pin connector block connected as
shown in Figure 1.
8.
Set the calibrator voltage to the positive test-point value in Table 9.
9.
Read the voltage from the DMM. Record the DMM reading as
output1
, and the calibrator output voltage as volt1, for later use.
10. 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.
11. Read the voltage from the DMM. Record the DMM reading as
output2
, and the calibrator output voltage as
volt2
. You now have two
pairs of data points, (
volt1
,
output1
) and (
volt2
,
output2
), where
volt1
and
volt2
are calibrator readings, and
output1
and
output2
are DMM
readings.
12. Convert the DMM voltage readings (
output1
and
output2
) to binary
readings (
binary1
and
binary2
) using the following equation:
Note
In both of the above equations,
output
is either
output1
or
output2
.
For example, using a 16-bit product such as a NI 6030E and obtaining
a DMM reading of –9.90000 V, you get the following results:
13. Record
binary1
with
volt1
, and
binary2
with
volt2
, for later use.
14. Repeat steps 5 through 13 for the remaining gain values you want to
measure on this channel.
15. Repeat steps 4 through 14 for the remaining channels you want to
measure.
binary reading for 16-bit E Series products (binary)
output
20
-----------------
⎝
⎠
⎛
⎞
2
16
×
=
binary
9.90000
–
20
----------------------
⎝
⎠
⎛
⎞
2
16
×
32440.32
–
=
=
