Multifunction DAQ
Photodetector irregularity with usb 6229
Hi everyone,
I am having an issue with my photodetector that I believe is a product of how I have my DAQ board configured. Setup is as follows:
Detector: Hamamatsu H9305 PMT (Normal output voltage range is 0-5V)
Labview 9
USB DAQ 6229
I have this configured in the NRSE mode for grounded sources (I assume the PMT is a grounded source since the output is a coax cable and the detector is grounded on the input side). Voltage out goes to the AIx, ground goes to AI SENSE. One thing I notice is that when I wire my signal ground into the AI SENSE, AI SENSE becomes connected to AI GND. I was under the impression that these should be isolated from each other in an NRSE measurement.
I am able to record voltage for the way I expect for a single measurement with very good repeatability. What worries me is inconsistency over a range of input signals - this detector should be extremely linear. The attached figure shows that my response jumps at a little less than 1 volt. This and the fact that my AI SENSE and AI GND are shorted together make me think something is wrong with my setup. Does this detector actually count as a floating source signal? Should AI-SENSE and AI GND be isolated from each other? Any help on this issue would be greatly appreciated.
Regards,
Mike
Regarding the grounding issue, it's simple enough to try the other settings, right? I don't think if it were a grounding issue that it would be working as good as it is. My question is: why do you expect the photomultiplier tube to be linear? Are you able to control light with that much precision? How are you testing it?
