Electronics > Beginners
Vpp from DSO in Square Wave
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vinlove:
This is a real newbie question I guess, but I have a guess for the answer, but I just want to clarify first, if my guesswer is correct or not.

I got this square wave of 100Hz generated from a multi meter, and connected that output to DSO.
The DSO showed a nice square wave, and it said Vpp: 3.5V, and Freq: 100Hz

But when I measure the voltage from the source of the wave with another DMM, there is nothing read on DCV. It is 0.00 volt.
Why does the DSC says Vpp from the source is 3.5V?
Jeroentjerad:
Because the squarewave is not DC. It is alternating anyway, like a sinewave.
vinlove:

--- Quote from: Jeroentjerad on July 05, 2019, 04:28:15 pm ---Because the squarewave is not DC. It is alternating anyway, like a sinewave.

--- End quote ---

Then why does DSO reads its Voltages?
mikerj:

--- Quote from: vinlove on July 05, 2019, 04:59:21 pm ---
--- Quote from: Jeroentjerad on July 05, 2019, 04:28:15 pm ---Because the squarewave is not DC. It is alternating anyway, like a sinewave.

--- End quote ---

Then why does DSO reads its Voltages?

--- End quote ---

Because DSOs are designed to calculate the voltages and frequencies of waveforms whether they are pure AC or have a DC offset.  Measure the waveform with your DMM set to AC.
Jeroentjerad:
The Vpp value of the signal, the maximal difference between the two extremes of it, is called the peak-to-peak value. Of you are measuring a sinewave the so called RMS value of the sine wave comes in play. You can measure that with the meter on AC, most of them can measure those signals and are labeled as "true RMS".
I think the meter cannot measure other than sinusoidal signals (in the ACV setting) because the formula used to do so uses a rotational factor. I suppose you know the difference between alternating and direct current? There are very many topics here explaining that.
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