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2520 detector bias voltage

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Joined: March 21st, 2011, 10:14 am
Country: United States

2520 detector bias voltage

Post by rpigraduate » March 21st, 2011, 10:29 am

I am using the 2520 for pulsed measurement of an LED. I am having an issue with the photodetector bias voltage. According to the circuit schematic, the bias voltage on the detector 1 line should have no correlation with the source, but when I change this bias, the output current levels also change. To diagnose this problem, I am using a resistor and oscilloscope to look at the waveforms..

I have hooked up the current source outputs of the 2520 to a 10 ohm resistor and am measuring the voltage across it with an oscilloscope. With 0 bias on detector one (D1), I can see my pulsed waveform, which looks very nice. Now I change the bias on D1 to -5V. My waveform read from the oscilloscope shifts in voltage. The shape still looks the same, but now I am reading a non-zero voltage/current all of the time. Nothing is connected to my D1 input.

I am very confused about this behavior, so any help or suggestions would be appreciated.

Dale C
Keithley Applications
Keithley Applications
Posts: 2847
Joined: June 10th, 2010, 6:22 am
Country: United States

Re: 2520 detector bias voltage

Post by Dale C » March 21st, 2011, 12:24 pm

Not sure if the bias and source are isolated or integrated.
I will check with design and post the result.

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