[sdiy] Measuring Vpp

Nicholas Keller niroke at tampabay.rr.com
Thu Jun 12 01:58:29 CEST 2014


John, 

Thanks for your suggestion, but that won't work for my scope.  The screen is tiny and digital with poor resolution.  I need an option that does not require the use of a scope, unless it is software-based and can utilize my sound card for signal input.

Nick



On Jun 11, 2014, at 7:43 PM, John Speth <jspeth at avnera.com> wrote:

>> The scope I have isn't great, more just for visual display of waveform
> than
>> accurate measurements.   I can't afford to get a proper scope, so I'm
> looking
>> for another way to calibrate outputs to 10Vpp and 20Vpp.  I looked up
> how to
>> do it with a DMM and it seemed more complicated than I had hoped. Does
> anyone
>> here have a suggestion of how to do this (easily) using a DMM, decibel
>> levels, or freeware?
> 
> A calibrated scope is nothing more than knowing the voltage difference
> between graticule hash marks.  You can calibrate that yourself with a
> known reference voltage for vertical and a known clock for horizontal
> (time).
> 
> The voltage reference can be attained by getting a voltage reference IC,
> wiring it up, and sending the voltage to your scope.  Then use some tape
> with carefully drawn hash marks.  Stick the tape to your scope screen and
> adjust your vertical gain so that you get a nice calibrated scale (for
> example, 1V per division).  Now you have a calibrated scope.  You'll need
> to recalibrate every time the vertical gain changes and maybe even every
> time you turn on your scope.  Be sure to verify your reference with your
> DMM for sanity.  You might need an op-amp circuit to gain up your
> reference voltage.
> 
> JJS
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