Calculating Peak-to-Peak Voltage from RMS Measurement: A Guide for Scientists

[luigihs]

A multimeter is used to measure a sinusoidal signal and reads 2V RMS; what is the peak-to-peak voltage of the signal? A mark will be deducted if you do not quote your answer to 2 significant figures.


This is my guess I am not really sure, there is not enough details I don't know how to get peak-topeak voltage of the signal


2 x 2 = 4

 

[rjnoonan]

volts rms are = to .707 of peak; so 1/.707 x 2 will give you peak. ptp is twice that.

 

[luigihs]

So.. 1.414 x 2 = 2.83 V? am I right?

 

[rjnoonan]

problem did not state whether 2vrms was peak or peak to peak. if peak, 1.414, if ptp
then 2.8

 

[luigihs]

Ok .. but if I have instead of 2V RMS is 4 RMS I just change the 1.414 x 4 right?

 

[rjnoonan]

Luigi, for a sine wave, .707 times peak = rms (peak); .707 times ptp = rms (ptp)
the question says volts = 2v rms but doesn't spec peak or ptp. is 2vrms peak or ptp?
we don't know. 2 answers.

 

[luigihs]

Luigi, for a sine wave, .707 times peak = rms (peak); .707 times ptp = rms (ptp)
the question says volts = 2v rms but doesn't spec peak or ptp. is 2vrms peak or ptp?
we don't know. 2 answers.

It doesn't say in the problem... only says that I have to find the peak-to-peak voltage of the signal

 

[rjnoonan]

since he is spec'ing a sine wave go ahead and assume we are looking at the full sinusoidal wave and using peak to peak. so answer will be 1.414 times 2vrms for
peak to peak voltage.

 

[luigihs]

Ok thanks :)

 

[SunnyBoyNY]

Luigi, for a sine wave, .707 times peak = rms (peak); .707 times ptp = rms (ptp)
the question says volts = 2v rms but doesn't spec peak or ptp. is 2vrms peak or ptp?
we don't know. 2 answers.

There is no such thing as peak-RMS or peak-to-peak RMS. The RMS value is a quadratic mean and thus all negative signal values are treated as positive signal values.

If RMS is 2Vrms, then the peak-to-peak voltage is 2.82V.

 

[gneill]

There is no such thing as peak-RMS or peak-to-peak RMS. The RMS value is a quadratic mean and thus all negative signal values are treated as positive signal values.

If RMS is 2Vrms, then the peak-to-peak voltage is 2.82V.

No, that would be the peak voltage. Peak-to-peak is twice the peak.

 

[SunnyBoyNY]

No, that would be the peak voltage. Peak-to-peak is twice the peak.

Agreed. Peak voltage is 2.82V and peak-to-peak voltage is 2*2.82V. My mistake.