Quick question about the oscilloscope app and maybe calibr

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lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Quick question about the oscilloscope app and maybe calibr

Post by lblaauw » Wed Jan 04, 2017 8:27 pm

Hi,

Quick question upon measuring a voltage (simple circuit with two 100k resistors in serial and 5v from red pitaya in), with a multimeter i measure aprox 2,34 volts now with with the scope application it shows 2.041v?

Am I missing something here or maybe the red pitaya needs calibration?

Any help, info or tips appreciated.

regards,
Leo

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Fri Jan 06, 2017 3:55 pm

No one any ideas ? ..

regards,
Leo

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Quick question about the oscilloscope app and maybe cali

Post by Nils Roos » Fri Jan 06, 2017 10:30 pm

If you measure an unexpected voltage from a known source, you should certainly try to calibrate your Red Pitaya (see here).

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Sat Jan 07, 2017 9:01 am

Hi Niels,

Well actually its not an unknown voltage its the first example from the elektor book about red pitaya soms know the voltage and als have measured with a multimeter. Just suprised me the pitaya measurement was about 0,35v apart from what the multimeter tells me.

Anyway thanks for your reply and i will give calibration a go.

Regards,
Leo

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Sat Jan 07, 2017 11:09 am

Niels,

So in the attachment picture is what I see if in the oscilloscope application i connect out1 to in1. The generator is set to 1v amplitude but still I see in the scope the amplitude on IN1 is .845v?
Capture.JPG
Pretty new to electronics and red pitaya, coming from a software background and a recent HAM operator so i might be totally doing the wrong thing or looking at it the wrong way though?

Thanks,
Leo
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Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Quick question about the oscilloscope app and maybe cali

Post by Nils Roos » Sun Jan 08, 2017 1:08 am

First try to reset the calibration settings to factory defaults - there's a menu item in the scope app for that. When I did that with a totally miscalibrated RP, it brought the measured input from 1.13V to 0.999V for a 1V DC generated output.

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Sun Jan 08, 2017 10:56 am

Hi Niels,

Just did the factory defaults for the calibration in the scop... now the measured voltage is even lower, 766mV.. Weirdnes all around not sure what else to try but suggestions welcome.

thanks and greetings,

Leo

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Quick question about the oscilloscope app and maybe cali

Post by Nils Roos » Sun Jan 08, 2017 1:34 pm

And what happens when you do the calibration procedure?

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Sun Jan 08, 2017 2:02 pm

Hi Nils,

I have shorted IN1 and IN2 and pressed calibrate. I have IN1 to 1v and IN2 to 20v btw not sure if that makes a difference. Previously it was and still is after calibration still hovering around 827mV.

regards and many thanks for your assistance.

Leo

lblaauw
Posts: 13
Joined: Sun Jul 03, 2016 10:42 am

Re: Quick question about the oscilloscope app and maybe cali

Post by lblaauw » Mon Jan 16, 2017 11:15 am

Just to anwser the solution to my own problem ;-)

Did a two step calibration through the oscilloscope app:
1. standard calibration with IN1 and IN2 shorted
2. LV/HV calibration with a known stable input voltage

Problem gone and Red Pitaya now nicely calibrated !

regards,
Leo

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