reading photodiode with USB 6009

[boise_bob]

I am trying to read voltage output from a photodiode using analog input on a USB DAQ 6009 from Labview.  I am able to read voltage from batteries using the DAQ, but when the photodiode is connected to the DAQ,  I get a noisy signal (see attached photo).  The photodiode works properly when I connect to a voltmeter (i.e voltage response with light).

Could this be a signal conditioning or impedace problem between DAQ and photodiode (spec sheet attached). 

Any suggestions would be appreciated.

Thanks

[AnalogKid2DigitalMan]

Looks like normal 50-60Hz powerline frequency from lighting (with some noise). A voltmeter will not respond as fast as your DAQ will. If you have an oscilloscope, you may want to connect that to the photodiode to see what the actual ouput is.

-AK2DM

[F._Schubert]

1. Use RSE measurement instead of Differential.

if this doesn't help: 

2. Redo your cabeling. Use a shielded twisted pair cable (connect shield to AI GND). Cables like that are mostly found for audio applications (the more expensive loadspeaker or microphone cables are nice).

Felix 

[Coq_Rouge]

It looks like 50 or 60 Hz to me. Put your sensor in a dark box and use battery powered light bulb. It could be that these fluctuations are caused by the fact that the your room illumination is powered by a 50/60 Hz AC source

[falkpl · Accepted solution]

You can also consider filtering your signal if there is too much 60Hz Noise.  You can either put a simple filter circuit on the input or use one of the many digital filters applied to your data shipped with labview.  This could help depending on the nature of the signal you are looking for (IE impulses, DC, decay curves ....)

[ajeetraj]

So I have the same case here, could you please tell me what helped you and how did you do it?

waiting for your reply.

thanks!