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Entry  Fri Apr 16 11:27:01 2021, Aidan, Update, 2um Photodiodes, 2um DC photodiode voltage weird drift with no incident power DC_2um_voltage_weirdness.png
    Reply  Fri Apr 16 13:05:05 2021, Aidan, Update, 2um Photodiodes, 2um DC photodiode voltage weird drift with no incident power IMG_2132.jpgFM30_31_w_latter_filtered.pngIMG_2134.jpgbias_bypassed.png
Message ID: 2556     Entry time: Fri Apr 16 11:27:01 2021     Reply to this: 2557
Author: Aidan 
Type: Update 
Category: 2um Photodiodes 
Subject: 2um DC photodiode voltage weird drift with no incident power 

[Aidan, Radhika, Nina]

We noticed that the DC channel readout (FM30) of the JPL A1 photodiode is drifting around. What we observe with no light on the photodiode, is the DC output drifiting around. It gets particularly bad when we apply voltage to other DAC channels.

For example, the attached plot shows the DC voltage from the photodiode as I change the set voltage to the laser diode driver. To be absolutely clear, the laser driver itself was completely powered off. I'm just varying the voltage going into the set point BNC connector on the back of it.

For reference, the set up is:

DAC (300mV bias) > relay > PD > relay  > FEMTO preamp (1000x gain) > ADC channel FM30

 

Attachment 1: DC_2um_voltage_weirdness.png  14 kB  Uploaded Fri Apr 16 12:34:00 2021  | Hide | Hide all
DC_2um_voltage_weirdness.png
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