re digital voltmeter how does it work mamishev alexander valentino avm sigma tamu edu wrote hello let me introduce a problem when i measure a sinusoidal wave voltage with a digital voltmeter using ac mode my output is an rms value a peak value over squared right when i measure a square wave in the same mode ac my output is equal to a peak value actually to the upper flat boundary of the wave i assumed that a digital voltmeter makes some kind of integration of the input value and divides it over the wave period right now i used it to measure the same square wave as above but distorted by high frequency harmonics ideally output should be the same but the output value was only about of the previous one why what is the nature of this output value what does the voltmeter actually measure and what does it show re rms readings unless the dvm says it s measuring rms it s probably average voltage the input is diode rectified and measured as dc if it says it s rms and but measures square triangle etc incorrectly it s measuring average and multipling by a correction that s only true for sine waves i e vave vrms if you want correct rms for most any waveform you need a true rms dvm dmm which literally does the root mean square calculation in either analog or digital circuitry related question less important to me what are advantages and disadvantages of digital voltmeters to compare with analog ones the last significant advantage of analog imo was being able to see the signal if it was changing over time e g checking electrolytic capacitors anymore most dmm have bargraphs etc that duplicate this thank you for your attention you could mail me your opinion at avm zeus tamu edu or open a discussion here i would appreciate either way alexander v mamishev power system automation laboratory phone office department of electrical engineering phone home texas a m university fax college station tx usa internet avm zeus tamu edu jeff gruszynski semiconductor test equipment systems engineer hewlett packard or t jeff hpmvd nsr hp com jeff hpuplca nsr hp com
