Frequency Generator not Outputting Correct Amplitudes?

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aiyabunni
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Frequency Generator not Outputting Correct Amplitudes?

Post by aiyabunni »

Hello,

I have a PicoScope 5243D and am using a TA375 100 MHz oscilloscope probe. I am using PicoScope 6 Beta to connect with it.

I haven't had any troubles with my PicoScope in the past but the other night my function generator went crazy. I noticed when I changed the amplitude of the signal generator on the signal generator window, the signal outputted did not change at all. The amplitude was stuck at 120 mV no matter what amplitude I set with the arrows. I had the function generator output connected to my probe with the probe on 10X. After a while of the generated signal not changing suddenly the signal generator window went crazy. I had not clicked anything but the amplitude changed by itself going up in increments to 2V then immediately down to 0V. I got scared so I shut down everything.

Ever since when I try and set the amplitudes in the function generator, it doesn't seem to match the output. For the two attachments below, I can kind of see how with 1V amplitude the 10X probe would read about 100 mV for the max. But with the 20 mV amplitude I dont understand how the max is around 6.

Is this how it's supposed to be with a 10X probe? I feel like I haven't noticed this difference before.

I appreciate any help/explanations I can get.

Thank you for your time.
Attachments
Screenshot from 2021-02-17 23-42-22.png
Screenshot from 2021-02-17 23-43-10.png

Gerry
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Joined: Mon Aug 11, 2014 11:14 am

Re: Frequency Generator not Outputting Correct Amplitudes?

Post by Gerry »

Hi aiyabunni,

Are you sure you don't have a connection problem. The first plot is just the input noise of the scope, not the 20mV sinewave output of the Generator. I would check your connections ,then set the SIg Gen to generate just a DC level output with a DC Average measurement of the output. Then start swapping between different levels to see if you have problems with the Sig Gen.

Also, what Linux distro is that (doesn't look like OSX)?

Regards,

Gerry
Gerry
Technical Specialist

aiyabunni
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Re: Frequency Generator not Outputting Correct Amplitudes?

Post by aiyabunni »

Hi Gerry,

Thank you for your response.
I have used the BNC output wires on a different picoscope before and they worked perfectly so I don't think it's a connection problem unless it's something with the probe?

Here are some more images doing what you suggested. At least I think this is what you were describing...is this the expected output?

I am using Ubuntu 18.04.5 LTS.

Thank you,
aiyabunni
Attachments
Screenshot from 2021-02-23 14-07-27.png
Screenshot from 2021-02-23 14-08-34.png
Screenshot from 2021-02-23 14-09-31.png

Gerry
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Posts: 927
Joined: Mon Aug 11, 2014 11:14 am

Re: Frequency Generator not Outputting Correct Amplitudes?

Post by Gerry »

Hi aiyabunni,

The offsets and amplification look OK, if you're using the x10 Probe switch i.e.:
The second screenshot would be correct because the signal offset is 100mV, which gets divided down to 10mV. and the third one because a 1V amplitude (i.e. 1V peak) is being divided down by 10 to ≈100mV peak, (i.e. ≈200mV p-p).
So, could you just confirm if you were using the x10 switch?

However, that is a lot of noise on the first and second waveforms.
Could you send in an image (or images) of how everything is hooked up.

Also, in your first comments the only part that could be a problem is when you said
After a while of the generated signal not changing suddenly the signal generator window went crazy. I had not clicked anything but the amplitude changed by itself going up in increments to 2V then immediately down to 0V
.Can you remember if it was randomly incrementing, with the Sig Gen output set to 2V, or not?

Regards,

Gerry
Gerry
Technical Specialist

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