Re: Measuring Ripple???

On Fri, 09 Jun 2006 21:00:18 GMT, DecaturTxCowboy <forgetit@xxxxxxxxxx>
wrote:

Phil Allison wrote:
"DecaturTxCowboy"

What he is saying is that a (typical) analog meter movement's needle will
be deflected (respond) proportional to the *average* current applied.
OK, that's what I thought he was saying, but something made me think for a
minute he might have been referring to something I was not even aware of.



** I certainly was.

YOU were NOT aware of the correct meanings of "true rms" or "rms
responding" .

It certainly would be more helpful of explaining the rational when
posting, instead of a terse comment. I still have no clue what you are
actually getting at.

So instead of playing twenty questions to get an answer from you, I'll
try I'll try an example.

I put a scope across the AC line and observe a 60 cycle sine wave that
is 340 volts peak-to-peak.

Now...the question is: If put a Simpson 260 across the AC line, will it
not read 120 volts?

The direct answer is yes, with some error if the line voltage is not a
pure sine wave, but is distorted. Every line frequency AC meter ever made
(he said boldly) was designed to read correctly when the waveform is a pure
sine wave (unless it's a specialty meter designed to read peak voltage, or
something like that). It's when the waveform is other than an undistorted
sine wave that errors arise. Some current DMM's can even read the correct
"true RMS" when a DC component is present, such as the unfiltered output of
a rectifier.


That's about as simply a way I can say that.

.

Relevant Pages

  • Re: multimeters
    ... Without True RMS, you can't measure all AC signals as accurately. ... wave - scaled up to display the exact rms value with sine wave signals. ...
    (sci.electronics.basics)
  • Re: Voltmeter Question !!!!
    ... value* of the input wave - allowing for frequency response limitations. ... The "true rms" value of a sine wave is 1.11 times the average rectified ...
    (sci.electronics.basics)
  • Re: anti-aliasing
    ... The adc will take a bunch of samples, ... If the sine wave is of a sufficently low frequency WRT to full sample time, then any given sub-section of that sine would be samples, giving obvious errors. ... If it is a complex waveform signal, that might not be a useable solution. ... "small" dithering of the sampling periodicity will not help; it might be useful when the input periodocity is near one of the harmonics of the sampling rate. ...
    (sci.electronics.design)
  • Re: I found the holy grail that explains audiophile beliefs
    ... steady amplitude sine wave it does not work with a decaying sine wave, like Cymbols clanging, unless the decay rate is slow enough to build up a number of samples. ... waveform can be thought of as a small section of a longer repeating waveform. ... While it may be reconstructed within reason, a side by side comparison of the original analog and the digitized output will show differences, distortion, phase delay, and some sideband spikes a KHz or so on either side of the desired waveform. ... The spikes were post digital filter so it could have been due to the switched capacitor clock getting through and causing strange things. ...
    (rec.audio.pro)
  • Re: Digital sine wave generation
    ... equal phase spacing, I'm very interested. ... generates a waveform that is a stepped sine approximation. ... Maybe I should've written "that do sine wave synthesis and do a good ...
    (sci.electronics.design)