40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  SUS Lab eLog  Not logged in ELOG logo
Message ID: 1834     Entry time: Tue Dec 3 09:50:18 2019
Author: Duo 
Type: DailyProgress 
Category:  
Subject: Interesting observation on noisemon debugging 

We have observed that the noisemon bug happens after it is powered on for about 1.5 hour. Noisemon has been powered on overnight and the following morning I came in and found

- Channel 1, 3, 4 bad (with signals like attachment 1. Green: normal behavior driven with 250 count, 10Hz signal. Brown: abnormal behavior with no drive)

- Then I used the oscilliscope and did the following on channel 4:

1. Connected channel 1 to measure the voltage between one side of C2 and GND.

2. Connected channel 2 to measure the voltage between another side of C2 and GND.

3. Use MATH on the oscilliscope to measure the voltage difference

- Then I found channel 4 is good! I did not turn the power off or do anything else.

- I repeated exactly the same procedure on channel 3 and it is repeatable.

- I left channel 1 as comparison and made attachment 2.

- Then I just use the probe of oscilliscope to connect one side of C2 on channel 1 to GND and got attachment 3, which channel 1 is good again.

I think this is a very strong hint that this whole problem is due to C2 charging up.

Attachment 1: Saturating.pdf  30 kB  | Hide | Hide all
Saturating.pdf
Attachment 2: diaggui.pdf  37 kB  | Hide | Hide all
diaggui.pdf
Attachment 3: Goodagain.pdf  39 kB  | Hide | Hide all
Goodagain.pdf
ELOG V3.1.3-