[sdiy] Measuring Vpp

Nicholas Keller niroke at tampabay.rr.com
Thu Jun 12 02:37:17 CEST 2014


Oren. 

That might work for me if I can't find a lazier way.  I'll look for a circuit I can power with my spare -/+12V supply and a breadboard. 

Nick



> On Jun 11, 2014, at 8:15 PM, Oren Leavitt <obl64 at ix.netcom.com> wrote:
> 
> 
> 
>> On 6/11/2014 6:58 PM, Nicholas Keller wrote:
>> 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
> 
> Hi Nick,
> 
> Another possibility is a simple level indicator circuit made of two comparators and two LEDs - one set at -5V, one set at +5V.
> 
> 
>> 
>> 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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