picoscope peak to peak measurement

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Hans de Vries
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picoscope peak to peak measurement

Post by Hans de Vries » Sun Mar 29, 2020 4:30 pm

Hi,
The output from my TTi function generator is set at 9.2Vpp. A Fluke 123B Industrial Scopemeter registers 6.503 Vrms, which is 9.2 Vpp.

The Pico registers 18.4 Vpp, which is twice the value measured independently by the TTi function generator and by the Fluke Scopemeter.

Please tell me why this is the case, and which value I should trust.

Thank you.

Hans de Vries
hansdevries@btinternet.com

NeilH
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Re: picoscope peak to peak measurement

Post by NeilH » Mon Mar 30, 2020 5:46 am

Hi Hans

Do you have a psdata file showing the captured signal from your generator?

Neil
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Hans de Vries
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Re: picoscope peak to peak measurement

Post by Hans de Vries » Mon Mar 30, 2020 9:00 am

Hi Neil. Thank you for your response.

I am not sure what a psdata file means. I just go by the textual information at the bottom of the screen which is confirmed by the numerical side bars that show the values of the peaks.

I am just mystified why there is a factor "2" between the input to the screen and the text/display on the screen.

I appreciate your assistance.

Best regards,

Hans

NeilH
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Re: picoscope peak to peak measurement

Post by NeilH » Tue Mar 31, 2020 7:04 am

Hi Hans

A psdata file is a file type that the data can be saved as in PicoScope 6 that would allow me to see your signal and your set up.

Neil
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Hans de Vries
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Re: picoscope peak to peak measurement

Post by Hans de Vries » Tue Mar 31, 2020 9:45 am

Hi Neil,
Thank you for trying to help me along.
However, I'm in no way computer savvy, even when you show me how, I'm likely to stumble.
I have downloaded Picoscope 6 and made no changes to it. I'm using the normal x10 probes and just look at the screen - and noticing the x2 multiplier of the amplitudes.

The x2 factor must arise from something that is obvious to an expert like you. Most likely, it stems from just one instruction in the Picoscope 6 data set. If you can go along with this idea, you may be able to tell me about the instruction (not necessary for me to know) and confirm that the real value is half the value written in the bottom lines.

I'll be happy then.

Best regards,

Hans

NeilH
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Re: picoscope peak to peak measurement

Post by NeilH » Tue Mar 31, 2020 10:12 am

Hi

Do you know what the output impedance of the function generator is?

Neil
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Hans de Vries
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Re: picoscope peak to peak measurement

Post by Hans de Vries » Tue Mar 31, 2020 11:30 am

Hi Neil,
Yes, the impedance is 50 Ohm.

Now, from the User Manual WMA-IB-HS of www.falco-systems.com I remember that with a load resistance of 50 Ohm the output is Vout=Vin and that with a load resistance of 100K the output is Vout=2 Vin.

In my case the input impedance of the amplifier (WMA-100) is 100K. That's where the factor x2 comes from.

Thank you, Neil, for pointing me in the right direction. I apologise for having claimed some of your precious time.

Best regards and best wishes with that virus,

Hans

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