USB-6009 coefficients for scaling

[Kling]

Hi, I'm currently using USB-6009. I'm using DAQmxReadBinaryI16 to read data and scale the binary data to volts. I use the function DAQmxGetChanAttribute to get the DAQmx_AI_DevScalingCoeff for each channel, I am using Single ended Analog input of 8 channels. However, I found the offset of my waveforms far below zero, I suspect that

the scaleCoef[0] which is far below zero that caused it.

scaleCoef[0] = -31.157441

scaleCoef[1] = 0.000638

scaleCoef[2] = 0.00 

I am using the polynomial functions of ax^2+bz^1+cx. Is this correct?

I feel that the scaleCoef[0] should read a very low value below 1.0. Which function should I use to get the correct scaleCoef. Please advice.

[Boon Chen]

Hi Kling,

 You can use the DAQmxGetAIDevScalingCoeff function to retrieve the device's scaling coefficients.

The polynomial you used is not correct, it should be the other way round ie. ax + bx^1 + cx^2...

You can refer to this KB for more information on scaling:

Is DAQmx Raw Data Calibrated and/or Scaled?

Best Regards,

Boon Chen

Applications Engineer

NI ASEAN