I am using PCI-6024

[rsr004]

E DAQ board to get analog signal. The signal seems to saturate at 10V after a minute and only after we change the AO Properties to Refernced Single Input does it come back to normal. Even then, it is not the same level as with Differential. Why is this so?The signal is from a Thor Lab DET 110 photodetector and this is converted to voltage. Earlier we were getting about 2 volts output with Differential setting.After we changed it to Referenced Single Input , the output has gone down to 0.2 Volts. Why does this happen?

[John N]

E DAQ board to get analog signal. The signal seems to saturate at 10V after a minute and only after we change the AO Properties to Refernced Single Input does it come back to normal. Even then, it is not the same level as with Differential. Why is this so?Hello,

It sounds like you will be able to just fix your connecctions and get good measurements.

The physical connections that you make for differential and single-ended measurements are not the same. If you are making differential measurements (which I recommend), then you will need to use channel pairs: ACH0 and ACH8, ACH1 and ACH9, and so on.

If you want more background information on this, we have several good tutorials on the zone website:
Field Wiring Considerations
Data Acquisition Fundamentals


The basic answer is that if you are using differential mode, then you must connect your input to two input channels. If you are using a single ended mode, then you will need to connect one lead of your voltage to an input channel, and one to either AIGND or AISENSE for referenced single ended or non-referenced respectively.

Hope this helps. If you want to contact NI directly, please come to http://www.ni.com/ask .

Best Regards,

John N
Applications Engineer
National Instruments