Actually, integrating the product of voltage and current gives the right answer. You just need to know where to put the probes.
Joe Smalley Rural Kitsap County WA Fiesta 48 volts NEDRA 48 volt street conversion record holder [EMAIL PROTECTED] ----- Original Message ----- From: "Victor Tikhonov" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, September 09, 2002 12:49 PM Subject: Re: Sometimes a PFC charger looks like an overunity device but it is not > The most accurate meters for these cases are probably calorimetric > (right term in English?) - a substance heated up by > the input power and you measure its temperature gradient over time > by a thermocouple. > > This eliminates wave form shapes, distortions etc. Pure power because > you measure a work the real power has produced. > > > Victor > > Joe Smalley wrote: > > > > Here at my shop, I have a machine that I have used to test transistors, heat > > sinks, capacitors and inductors to see how efficient they are under working > > conditions in a flyback converter. Rich Rudman was impressed that I could > > generate 90 amps at 400 volts off a 8 amp breaker on a 120 VAC outlet. It > > took several explanations to get him to understand how it worked. Since > > then, he has been very careful about HOW things are measured and HOW the > > data is reduced. We are very cautious about efficiency claims on our > > chargers because of this effect. Two different meters that read the same > > numbers in one situation will read different numbers when used on the PFC > > chargers. We need better instrumentation to reliably measure the efficiency > > numbers with adequate resolution and repeatability. > > > > Just because your meter reads a number does not mean that there is that much > > voltage, current or power being transferred. Crest factor, phase > > displacement, and harmonic distortion all play havoc with trying to read > > true power. > > > > Joe Smalley > > Rural Kitsap County WA > > Fiesta 48 volts > > NEDRA 48 volt street conversion record holder > > [EMAIL PROTECTED] > > > > > Actually NIST tested his device at the insistence of the Patent > > > Office. I read the report. The key to his device is called the "crest > > > factor." Typical AC voltmeters are built to correctly read a sine wave. > > > When you feed in a wave with a drastically different shape, you get > > > incorrect readings. The ratio of the RMS value to the peak value of a > > > waveform is called the crest factor. The waveforms that came out of the > > > Newman machine had a crest factor greater than a typical voltmeter could > > > handle. Thus, the voltmeters would read higher than the actual RMS value > > of > > > the waveform. > > > > > > When you use a Radio Shack voltmeter, it appears you are getting > > > more power out than you are putting in. If instead, you use a high-speed > > > scope for the measurement, it is obvious that you are putting in a lot > > more > > > power than is coming out. >
