Amplitude is 1/3 of what it should be?

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TSChris
Posts: 7
Joined: Fri Aug 29, 2014 6:45 pm

Amplitude is 1/3 of what it should be?

Post by TSChris »

After assembly, everything works great, EXCEPT the amplitude. I always see 1/3 of whatever amplitude I get.
I checked this with using an oscilloscope, and all the waveforms, frequencies, voltage offsets, work fine.
Is there something I am missing?

Chris
jye1
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: Amplitude is 1/3 of what it should be?

Post by jye1 »

Did you have any loading at the output?
TSChris
Posts: 7
Joined: Fri Aug 29, 2014 6:45 pm

Re: Amplitude is 1/3 of what it should be?

Post by TSChris »

Hello.
Tested with no load other than a scope. (1 meg impedance)

Chris
jye1
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: Amplitude is 1/3 of what it should be?

Post by jye1 »

Could you please explain how you read your amplitude measurement? Was it measured by counting divisions on scope graph or from some digits read-out?
TSChris
Posts: 7
Joined: Fri Aug 29, 2014 6:45 pm

Re: Amplitude is 1/3 of what it should be?

Post by TSChris »

Hi.
The measurements were taken by counting scope divisions and also by the readout from a multi meter.

Chris
jye1
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: Amplitude is 1/3 of what it should be?

Post by jye1 »

The displayed amplitude setting is peak-to-peak value. The RMS value for a sinus siganl, i.e. (Vpp/2) * 0.707, is very close to 1/3 of Vpp. If voltage was read from volt-meter you likely got RMS value. But from scope you should easily get p-p value. Did the measurements you got (from scope and meter) match?
TSChris
Posts: 7
Joined: Fri Aug 29, 2014 6:45 pm

Re: Amplitude is 1/3 of what it should be?

Post by TSChris »

I was able to determine what the problem was. Turns out the power supply was defective. Swapped in a new one ant it's working fine. Thank you for your help!
Chris
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