03-15-2017 01:01 AM
Hi Everyone,
I am having a small problem that has troubled me for awhile now.
I use LabVIEW 2016 and 7853r FPGA card. I have 4 stable signals from 4 different femto preamplifiers hooked up to a quadrant photodiode. I feed the signal to labVIEW through SCB-68 connector. I use SHC68-68 RMIO cable to connect the SCB-68 to the Chassis (NI PXIe-1062Q).
My problem is, when I check the signals via a multimeter or oscilloscope, I get a stable signal, but when I check the signal in LabVIEW FPGA using the code attached the signals fluctuates a lot, sometimes giving negative values. What could be the problem?
Any hint or ideas will be highly appreciated. Thank you.
Opuk
03-15-2017 02:26 AM
Could you provide some examples how the measurement looks like and how it should look like (as seen with the oscilloscope)?
The issue might be with the termination (RSE/NRSE) of the input for example.
03-15-2017 05:45 AM - edited 03-15-2017 05:48 AM
I am also seeing you are not applying a scale to the reading. You are just seeing the actual ADC bits. Any little noise will cause those bits to toggle. If you applied a proper scaling, that toggling might not look so bad.
V = Count*10/32767
03-22-2017 12:43 PM
Helo Nikodem,
Thank you for your response to my question. Attached please find the sampled measurements for my data. I expect the data to be a constant but the fluctuation is just crazy.
Kind Regards,
Opuk
03-22-2017 12:51 PM
Hi Crossrulz,
Thank you for finding time to respond to my question. I have tried applying a scaling as suggested but in vain.
Thank you.
Kind Regards,
Opuk