Noise and voltage reading problem

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wiciu15
Posts: 4
Joined: Thu Feb 01, 2018 6:22 pm

Noise and voltage reading problem

Post by wiciu15 »

I assembled dso150, and i have a problem with noise and voltage measurement. No matter if I'm in GND, DC or AC coupling there is high 2kHz noise, which makes my readings wavy and not accurate. Also I can't calibrate the vpos because after i do it the trace is going away(after some time) from center/yellow arrow. It messes up my voltage readings, only Vpp is accurate. Voltages on analog board are ok(V+ and V- are a bit low, about 7.5v and -6.5V). My software version is 064, board number 109-15000-00E1. Also C3 and C5 regulation don't seem to make any difference in shape of a test wave. Sensel0-3 signals are also OK.

I made a video to show some more about my problem: https://www.youtube.com/watch?v=iK8eN5_mOF0. In about a minute trace gone down by about 1 division
jye1
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: Noise and voltage reading problem

Post by jye1 »

What kind of power supply did you use? It is suggested to check power supply and the negative voltage generator (U5 and related parts on the analog board).
wiciu15
Posts: 4
Joined: Thu Feb 01, 2018 6:22 pm

Re: Noise and voltage reading problem

Post by wiciu15 »

9V battery, V+ and V- are kinda low. Bought even better branded battery, and the problem is still here. I measured that when I power on the DSO, battery voltage drops about 1V, a bit too much for a 120mA current?
jye1
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: Noise and voltage reading problem

Post by jye1 »

I guess you should have an "E" version (or F version) analog board. Please check C11 (replace it if you have another one). If you have the older C version analog board please check C13 and C14. The board version is the last letter in its part number. The number read like this: 109-15001-00X.
wiciu15
Posts: 4
Joined: Thu Feb 01, 2018 6:22 pm

Re: Noise and voltage reading problem

Post by wiciu15 »

Soldered new one and problem remains :( i have F version of the board
wiciu15
Posts: 4
Joined: Thu Feb 01, 2018 6:22 pm

Re: Noise and voltage reading problem

Post by wiciu15 »

Plugged it to a lab bench @9V and working like a charm, turned out it was happening because of the voltage drop of 9V battery.
Thanks for help, thread to be closed
Arnoldus
Posts: 15
Joined: Fri Dec 29, 2017 4:04 pm
Location: The Netherlands

Re: Noise and voltage reading problem

Post by Arnoldus »

May I give you a tip? I use this '9V' 300mAh NiMH battery (8,4V) from Conrad without any problem:
https://www.conrad.nl/nl/oplaadbare-9v- ... 05467.html
It remains most of the discharge time above 8V, and it runs at least 2 hours before charging is required.
(The scope is going weird below 7.5V ) And a charged spare battery can be handy....
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