02-02-2009 05:18 PM
Hi,
I have a USB-6225 and I'm trying to measure the voltage across a current sense resistor with the ai0 differential input.
I created the task in C with the following call
DAQmxCreateAIVoltageChan(taskHandle,"Dev1/ai0","",DAQmx_Val_Diff,-0.2,0.2,DAQmx_Val_Volts,NULL));
I used the range -0.2 to 0.2 because that was the smallest input range for this DAQ with 16 bit accuracy.
The voltage across the resistor is connected to terminals 1 and 17 in the DAQ. According to the docs, these are the correct terminals for a differential input to "Dev1/ai0"
The actual voltage accross my resistor is approx 0.001 Volt, but the call to DAQmxReadAnalogF64 is returning numbers around 0.123 Volts.
What am I doing wrong?
Thanks,
Hans
02-03-2009 06:47 PM
Hello Hans G,
I have a question about your setup and something I would like you to try.
Any other information about your application that could be affecting your measurements would be useful in diagnosing this problem.
Regards,
Dan King