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

AI Thread Summary
The discussion revolves around measuring noise from a receiver using a multimeter set to read DC voltage with a bandwidth of 10 kHz, while the noise is initially measured by an RMS voltmeter at 100 kHz, yielding a reading of 2 mV. One participant calculates that the multimeter reading would be 0.2 mV due to the reduced bandwidth. However, it is clarified that RMS and DC values differ when measuring varying AC signals, as a DC meter measures the average value, which can be zero for symmetrical waveforms like sine or square waves. Therefore, the average value of the noise, considered as an AC signal, would be zero when measured with a DC meter. The discussion highlights the importance of understanding the differences between RMS and average values in voltage measurements.
chipmunk22
Messages
15
Reaction score
0
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
 
Physics news on Phys.org
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! ;)
 

Similar threads

Odd multimeter readings with AC->DC wall adapter
Replies
8
Views
4K
RMS value secondary voltage electronic halogen transformer
Replies
1
Views
2K
Mystery Voltage: Investigating a Strange Phenomenon in MHD Testing
Replies
6
Views
1K
Does the voltage reading across a rotating DC motor decrease due to back EMF?
Replies
7
Views
5K
Understanding Output and Input Resistance of an Op Amp in a Lab Setting
Replies
1
Views
2K
Dc Circuits - Voltmeter/ammeter
Replies
8
Views
14K
What Could Cause Odd Failures in a Solid State Relay?
Replies
4
Views
7K
What is RMS Watts? Understanding AC Signals & DC Conversion
Replies
5
Views
19K
Hydrogen-Boron Plasma Toroid Fusion
Replies
4
Views
7K
Hydrogen-boron High Density Plasma Toroid Fusion
Replies
3
Views
4K

Hot Threads

Recent Insights

Back
Top