NI 9144 User Guide and Specifications
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© National Instruments
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71
NI 9233 Calibration Data
The NI 9233 has four input channels with a fixed gain. The inputs are AC-coupled, so calibration
is done with a sine wave rather than with DC signals. The specification derivations are based on
calibration at 250 Hz, acquired at 25 kS/s. The AC response (flatness) changes with both input
frequency and sample rate; therefore, calibrating at different signal frequencies or at different
sample rates gives different results.
Each channel has an associated LSB weight, which is the number of volts per bit, and an offset.
Note
LSB weight is referred to as Gain in the object dictionary.
The calibration data is stored in a U32 array, though each Offset field (subindex 1, 3, 5, and so
on) should be interpreted as a signed value.
Use the calibration coefficients with the following equation to generate corrected data:
NI 9234
The vendor configuration extensions for the NI 9234 are listed in Table 73.
Table 72.
NI 9233 Scan List Format
Coefficient
Representation
Units
Default Value
LSB Weight
Unsigned
pV/LSB
0x0009D292 (643.73 nV/bit)
Offset
Signed
nV
0x00000000 (0 nV)
Table 73.
NI 9234 Vendor Configuration Extensions
Index
Sub
Type
R/W
Description
0x2002
0
U32
R/W
Configure Module, default = 0x06
0x2100
0
ARR:U32
—
Calibration = 16
1
R
Ch0 Offset
2
R
Ch0 Gain
3
R
Ch0 Offset
...
—
—
8
R
Ch3 Gain
9
R
External Ch0 Offset
...
—
—
Calibrated_Data =Binary_Data LSB_Weight
×
Offset
–
