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NI 9144 User Guide and Specifications
The calibration data is stored in a U32 array, though each offset field should be interpreted as a
signed value.
The NI 9219 returns calibrated 24-bit (padded to 32-bits) AI data for all modes and ranges.
To convert raw data into engineering units use the following formula:
y
=
m
×
x
+
b
where
b
represents Offset based on range of the device: such as, -60 for ± 60 V Voltage
Measurement Range
m
represents Gain (Full-Range/(2
24
)): such as, 120/(2
24
) for ± 60 V Voltage
Measurement Range
NI 9219 Configuration Commands
There are eight configuration commands for the NI 9219. Eight configuration commands must
be sent for each of the four channels. This is true even if you are only using a subset of the
four channels. Each of the eight configuration commands is 1 Byte, each configuration
command is followed by a data Byte, and then by a CRC value, which is 1 Byte. Hence,
3 Bytes × 8 commands × 4 channels = 96 command bytes (held in 32 entries in the object
dictionary).
Data in the object dictionary is held in LSB format, so the value 0x12345678 is represented in
memory as the series of bytes 0x78, 0x56, 0x34, 0x12. The command word format is shown in
Table 56.
Table 55.
NI 9219 Calibration Data
Coefficient
Representation
LSB Weight
Unsigned
Offset
Signed
Table 56.
NI 9219 Command Word Format
Bits
Field
31..24
Reserved
23..16
CRC
15..8
Configuration Data
7..0
Configuration Command
