There is a device called a Kill a watt, that is a plug in kWh meter, should be avalible at big hardware stores.
http://www.killawattplus.com On Sun, Oct 4, 2009 at 6:57 PM, Eric Lemmon <wb6...@verizon.net> wrote: > Yeah, that is a big issue with those big and heavy ferroresonant power > supplies from GE and Motorola. At low loads, they are incredibly > inefficient, with very low power factors- meaning the volt-amperes are much > higher than the watts. Proof of this statement is found in the Files > section of this group, in my Power Supply Load Test folder. > > You pay for electric energy in kilowatt-hours, kWh, not for volt-amperes. > Regardless of what the ammeter reads, the Kill-A-Watt reading of 43 watts is > what counts. If we assume that the repeater sits idle for 24 hours and > consumes 43 watts, that is 1.032 kWh per day- probably 15 cents worth. I > have one of those Kill-A-Watt meters, as well as some spinning-disk meters, > and they agree very closely. > > Electricity suppliers don't like low power factors, because even though the > power consumption may be low, the utility must build their infrastructure to > supply those reactive amperes, meaning bigger generators, transformers, and > power lines. Large industrial customers are often penalized for low power > factor, to help pay for the additional capital equipment that must be > installed to supply reactive amperes. That's why new commercial gear is > using power-factor-corrected switchmode power supplies. The definition of > "high power factor" varies, but most utilities want PF to be above 0.9. > > It should be emphasized that one cannot determine power consumed (watts) by > separately measuring volts and amps. Separate measurements result in > volt-amperes, which is also called "apparent power." To measure true power, > one must use a wattmeter. A mechanical wattmeter is called an > electrodynamometer, and is a meter that has two coils- instead of one coil > and a permanent magnet. One coil is connected in parallel with the load, > and is energized by voltage. The other coil is much heavier and is > connected in series with the load, and is energized by current. The torque > on the meter movement is the instantaneous sum of voltage and current in > phase, result in a deflection indicative of power. An electronic wattmeter > uses a circuit element known as a four-quadrant multiplier, meaning that the > comparison of voltage and current is continuous through 360 degrees. I have > just such an instrument, a WD-767 digital wattmeter made by VIZ. It can > display true-RMS volts, true-RMS current, and true power in watts. Very > handy! > > 73, Eric Lemmon WB6FLY > > > -----Original Message----- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mike Morris WA6ILQ > Sent: Sunday, October 04, 2009 6:10 PM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] Spinning disk wattmeter... > > > > A ham I know is doing some research and needs to > locate a spinning disk KWH meter, with socket, cheap > or free... > > If he turns up something interesting it will end up as a > repeater-builder article. > > He wrote: > >>My concern is that the cabinet I had here last year measured at idle >>1.5 amps at 120V (180VA) yet also only measured 43 Watts with >>the Kill-A-Watt meter. I am looking for another device to tell me what >>the electric company is actually seeing and billing. Might one of your >>connections have an extra single phase KWH meter in the junk box? > > I suspect he has a situation involving power factor. > > Mike WA6ILQ > > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
