What's reading for multimeter set to read dc voltage and bandwidth of 10khz

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SUMMARY

The discussion centers on the measurement of noise from a receiver using an RMS voltmeter with a bandwidth of 100 kHz, which reads 2 mV. A participant calculated the expected reading for a multimeter set to measure DC voltage with a bandwidth of 10 kHz as 0.2 mV, based on the bandwidth ratio. However, it was clarified that RMS and DC values differ when measuring AC signals, as a DC meter measures the average value of an AC signal, which can be zero for symmetrical waveforms. Thus, the reading on a DC voltmeter connected to an AC signal generator would be zero, highlighting the distinction between RMS and average values.

PREREQUISITES
  • Understanding of RMS (Root Mean Square) voltage measurement
  • Knowledge of AC (Alternating Current) versus DC (Direct Current) voltage
  • Familiarity with multimeter operation and bandwidth settings
  • Basic concepts of signal waveforms, particularly sine and square waves
NEXT STEPS
  • Research the principles of RMS voltage and its calculation methods
  • Learn about AC signal characteristics and their impact on DC measurements
  • Explore the functionality and limitations of multimeters in measuring AC signals
  • Study the differences between average value and RMS value in signal analysis
USEFUL FOR

Electronics engineers, technicians working with signal measurement, and students studying electrical engineering concepts will benefit from this discussion.

chipmunk22
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Happened to come across this qn:

Noise from receiver is measured by rms voltmeter with bandwidth 100khz, and voltmeter reads 2mV. what will be the reading for multimeter set to read dc voltage and bandwidth of 10khz?

My ans is 10/100 x 2 = 0.2mV. cos smaller bandwidth reduced by a factor of 10.

Can anyone comment whether my answer is correct? tks
 
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Read the question carefully - in particular, the abbreviations "rms" and "dc".
 
so u mean the voltage reading shdnt change? since rms value and dc value are the same.
 
RMS and DC are not the same if you are measuring an voltage that varies with time.

A DC meter measure the average (mean) value of an AC signal, which is zero for a symmetrical wave form like a sine wave or a square wave.

Connect a DC voltmeter to a low voltage AC signal generator sometime, and see what reading you get - zero.

The "noise" in the question is basically an AC signal so its average value measured on a DC meter will be 0.

Check out what "root mean square" means, and how it is different from "mean" or "average".
 
Oh now i get it. Thanks for the explanation! ;)
 

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