HP HP-Bench-Briefs-1973-11-12 free download

File name HP-Bench-Briefs-1973-11-12.pdf

`e VOLUME 13 NUMBER 5 NOV/DEC 1973 AC ANALOG then our AC signal has an RMS or ef- amplified or attenuated, rectified by fective value of 1 volt. the diode bridge and fed to the meter. VOLTMETERS The meter then responds to this recti- In addition to its RMS value, a wave- by Harry Logan form also has a peak and average vol- fied average or DC value. tage value. See Figure 1. The average value of a sine wave is zero, so when we say average re- AC Analog voltmeters are one of the sponding we mean the rectified aver- most popular electronic measuring in- age or DC component after rectifica- struments in use today. They are used tion. This DC component deflects a ov d'Arsonval (moving coil) meter to indi- to measure the RMS voltage of the many waveforms commonly found in cate the RMS value of a sine wave. electronics. See Figure 2. This article will provide you with the ba- This sine wave has an RMS value of 1 sics of AC analog voltmeters. It will volt. Its peak value is 1.4 times its give you a better understanding of RMS value, or 1.4 volts. Its rec- their operation, allowing you to select tified average or DC value is .636 the right one for your particular mea- times the peak or .9 volts in the above surement. example. The RMS or root-mean-square vol- AC voltmeters are designed to re- Flgure 2. Average tage is measured because this value spond to one of these three values. responding gives us the most information about This classifies the meters into true voltmeter the waveform. The RMS voltage is RMS responding, average re- equivalent to a DC voltage which pro- sponding and peak responding. The The average responding meter is the duces the same heating effect as the average and peak responding volt- most popular and economical type of AC signal being measured. For meters are designed to measure only AC voltmeter. Its voltage scale example, 1 volt of DC across a 1 ohm sine waves. has been made to