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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.

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:

10.000 kS/s

1

00101

10

0x96

2.56 MHz

6.250 kS/s

1

01000

10

0xA2

1.60 MHz

5.000 kS/s

1

01010

10

0xAA

1.28 MHz

3.333 kS/s

1

01111

10

0xBE

853 kHz

3.125 kS/s

1

10000

10

0xC2

800 kHz

2.500 kS/s

1

10100

10

0xD2

640 kHz

2.000 kS/s

1

11001

10

0xE6

512 kHz

Table 45.  NI 9233 Scan List Format

LSB Weight

Unsigned

pV/LSB

0x0009D292
(643.73 nV/bit)

Offset

Signed

nV

0x00000000 
(0 nV)

Table 44.  NI 9233 Calibration Data (Continued)

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