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Scaling NI 9225 from RAW I32 to SGL numbers

Can someone please explain how I can convert raw integer data acquired from a NI 9225 voltage sensor to true voltages?

For the simulatneous AI in GPIC we used  (20/4096)* I16... what would its equivalent be for NI9225 which is a 24-bit voltage sensor that can measure upto 300Vrms?

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The NI 9225 has a typical input span of 850 Volts, so multiply the integer value by 850/2^24 to do the conversion to Volts.

However, the NI 9225 is calibrated at the factory to a NIST calibration reference. Offset and gain values for each channel are stored in an EEPROM on the module. When you read using Calibration Mode = Calibrated, the module applies this NIST calibration scaling for your voltage reading. This dramatically improves the accuracy of the module. Therefore, I recommend against using the RAW integer reading mode with this module.

You can find a shipping example for the module here:

C:\Program Files (x86)\National Instruments\LabVIEW 2015\examples\CompactRIO\Module Specific\NI 9225\NI 9225 Getting Started\NI 9225 Getting Started.lvproj

If you do want to read in Raw integer and do the scaling yourself, you can use the FPGA I/O Property Node to read the LSB Weight and Offset values for each channel. Then follow this online help topic (Converting and Calibrating CompactRIO Analog Input Values) for instructions on how to do the conversions.

2-16-2016 4-49-16 PM.jpg

By the way, you can go here to download the NIST traceable calibration sheet for your module using its serial number.

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