Calculating Peak-to-Peak Voltage from RMS Measurement for Scientists

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Discussion Overview

The discussion revolves around calculating the peak-to-peak voltage from a given RMS measurement of a sinusoidal signal, specifically addressing the ambiguity in the problem statement regarding whether the provided RMS value refers to peak or peak-to-peak voltage. Participants explore various methods and interpretations of the calculations involved.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the peak-to-peak voltage can be calculated as 2 times the RMS value, leading to an initial guess of 4V.
  • Another participant states that RMS is equal to 0.707 times the peak voltage, implying that to find the peak voltage, one should use the formula 1/0.707 times the RMS value.
  • A subsequent reply calculates the peak voltage as 2.83V based on the earlier formula.
  • Some participants note the lack of clarity in the problem regarding whether the 2V RMS is peak or peak-to-peak, leading to different interpretations and calculations.
  • One participant asserts that for a sine wave, the RMS value can be derived from both peak and peak-to-peak values, but emphasizes that the problem does not specify which is applicable.
  • Another participant suggests assuming the full sinusoidal wave and calculating the peak-to-peak voltage as 1.414 times the RMS value.
  • There is a correction regarding the definition of RMS, clarifying that it is a quadratic mean and does not directly equate to peak or peak-to-peak values.
  • Some participants express confusion over the terminology, indicating that there is no concept of "peak-RMS" or "peak-to-peak RMS," and clarify that if RMS is 2V, the peak-to-peak voltage would be calculated as 2.82V.
  • One participant acknowledges a mistake in their earlier calculation, confirming that peak voltage is 2.82V and peak-to-peak voltage is twice that value.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the interpretation of the RMS value as either peak or peak-to-peak, leading to multiple competing views and calculations throughout the discussion.

Contextual Notes

The discussion highlights limitations in the problem statement, particularly the lack of specification regarding whether the 2V RMS is peak or peak-to-peak, which affects the calculations and interpretations presented by participants.

luigihs
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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
 
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volts rms are = to .707 of peak; so 1/.707 x 2 will give you peak. ptp is twice that.
 
So.. 1.414 x 2 = 2.83 V? am I right?
 
problem did not state whether 2vrms was peak or peak to peak. if peak, 1.414, if ptp
then 2.8
 
Ok .. but if I have instead of 2V RMS is 4 RMS I just change the 1.414 x 4 right?
 
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.
 
rjnoonan said:
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
 
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.
 
Ok thanks :)
 
  • #10
rjnoonan said:
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.
 
  • #11
SunnyBoyNY said:
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.
 
  • #12
gneill said:
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.
 

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