Use the following equation in the host VI to convert binary analog input values to calibrated engineering units:

  • Input Engineering Units = (Binary Value × LSB Weight – Offset)[1]1 When converting and calibrating data acquired from the NI-9203 in ±20 mA range, the equation is <codeph>Input Engineering Units = ((Binary Value – 32768) × LSB Weight – Offset)</codeph>.
Where
  • Binary Value is the signed or unsigned value returned by the FPGA I/O Node
  • LSB Weight is the value returned by the LSB Weight property
  • Offset is the value returned by the Offset property.

The LSB Weight and Offset units differ per module.

To convert to calibrated engineering units, use the FPGA I/O Property Node to read the LSB Weight and Offset properties. If you do not want to read the LSB Weight and Offset values from the module, convert to uncalibrated engineering units. Use the following values for Offset and LSB Weight:

Offset = 0[2]2 When calculating engineering units for the NI-9203 in ±20 mA range, Offset = 20 mA.

LSB Weight = Typical Input Span ÷ 2ADC Resolution

Where

  • Typical Input Span value is listed in the following table for each module.
  • ADC Resolution value is the ADC resolution of the module. Refer to module documentation to obtain this value.
Table 38. C Series Module Typical Input Span
Module Typical Input Span
NI-9201 21.06 V
NI-9203 21.56 mA (unipolar), 43.12 mA (bipolar)
NI-9205 20.8 V
NI-9206 21.5 V
NI-9215 20.8 V
NI-9216 100 Ω RTD
NI-9217 100 Ω RTD
NI-9218 Varies by mode; refer to the following table NI-9218 Typical Input Span
NI-9220 20.8 V
NI-9221 125 V
NI-9222 21.2 V
NI-9223 21.2 V
NI-9225 850 V
NI-9226 1,000 Ω RTD
NI-9227 29.954 A
NI-9229 125.28 V
NI-9230 63 V
NI-9232 63 V
NI-9234 10.2 V
NI-9235 52.6 mV/V
NI-9236 52.6 mV/V
NI-9237 50 mV/V
NI-9238 1.25 V
NI-9239 21.04 V
NI-9246 62.5 A
NI-9247 294 A
NI-9381 5 V
Table 39. NI-9218 Typical Input Span
Channel Mode Typical Measurement Range
±16 V ±16.3 V
±20 mA 24.4 mA
±22 mV/V Bridge 22.1 mV/V
±5 V IEPE 5.33 V
±60 V ±62.1 V
±65 mV 73.5 mV

1 When converting and calibrating data acquired from the NI-9203 in ±20 mA range, the equation is <codeph>Input Engineering Units = ((Binary Value – 32768) × LSB Weight – Offset)</codeph>.

2 When calculating engineering units for the NI-9203 in ±20 mA range, Offset = 20 mA.