SCXI-1520 Calibration Procedure
8
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operating within specifications. Return it to NI for repair. For more
information about how to contact NI for repair, refer to the
Signal
Conditioning Technical Support Information
document.
1.
Read the
2.
Connect the DAQ device to the SCXI-1520 using an SCXI-1349 cable
adapter and a 68-to-68-pin cable.
3.
Connect the DMM to the appropriate excitation output terminals,
starting with channel 0. Refer to Table 1 to determine which pins
on the 96-pin front connector correspond to the positive and negative
excitation terminals of the specified channel. For example, the positive
excitation terminal for channel 0 (P0+) is pin C30. The negative
excitation terminal for channel 0 (P0–) is pin B30. If you are using
an SCXI-1314 terminal block, connect the DMM to the P0+ and P0–
output terminals of the SCXI-1314.
4.
Call
SCXI_Set_Excitation
to set the excitation voltage to the
desired value. Set the following parameters:
•
SCXIchassisID
—The value assigned by MAX
•
moduleSlot
—1
•
moduleChan
—The channel number from step 3
•
excitationType
—2
•
excitationValue
—The excitation value that you want to measure.
Refer to Table 3 for a list of valid values.
SCXI_Set_Excitation
returns a 32-bit floating-point number
called
actualExcitationValuePtr
. This number was stored in the
SCXI-1520 EEPROM when the module was last calibrated, and
represents the voltage excitation measured at that time. Record this
value as
V
exe
.
5.
Read the voltage from the DMM and record it as
V
exm
. You will use
V
exm
to verify the voltage excitation and, if necessary, to calculate new
calibration constants in the
Adjusting Calibration Constants
6.
Compare
V
exm
from step 5
to the upper and lower limits in Table 2.
If
V
exm
is within these limits, the module has passed this portion of the
test. If
V
exm
is outside these limits, the module is not operating within
specifications. Return it to NI for repair.
7.
Divide
V
exe
from step 4 by
V
exm
from step 5.
If the resulting value is
between 0.999 and 1.001, the calibration constants are within the
required specifications. Do not use 0.0 V excitation for this step.
8.
Repeat steps 4 through 7 for the remaining excitation levels you want
to test on the module.
9.
Repeat steps 3 through 8 for the remaining channels you want to test
on the module.