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Kill-A-Watt Power Meter Report Terry Fritz March 11, 2003
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After hearing of the “Kill-A-Watt” $50 power meter that could measure voltage (true RMS), current (true RMS), power (real), power factor, VA, and KWH with 0.2% accuracy. I got one from Radio Shack (#63-1152) to try out. They are sold by many on-line retailers too. Search on the key word “Kill-A-Watt”. It is a 120VAC 15 amp unit with the usual world wide safety approvals.
The unit is just a simple plastic box that plugs directly into an outlet on one side and has a plug on the other side. It has five buttons to quickly and easily select the functions.
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Of course, what counts is does it really work? To test it, I hooked it up with a Pearson 411 current monitor, Tektronix P5205 differential voltage probe, and a Tektronix 3012 Digital scope.
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For the first test, I simply plugged it into a 250W flood lamp. This is what the scope said:
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Ch1 50.0 V |Ch2 1.00 A M20.0ms A Chi I 0.00 V
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254.6 Watts 119 Volts 2.164 Amps
The Kill-A-Watt read:
254 Watts
118.3 Volts
2.13 Amps
252 VA
59.9 Hz
1.00 PF
Very Good! Some small error, but far below what one would care about.
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Next I tried a 1/4 HP induction motor for a spark gaps that has four flats ground into the rotor: The scope says:
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Ch1 50.0 V |Ch2 5.00 A M20.0ms A Chi I 0.00 V
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161 V 2.00 V
74.4 ° -74.4 °
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5.00 A M4.00ms A Chi I 0.00 V
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119 Volts 4.960 Amps 179.3 watts COS(74.4) = 0.264 PF 119 x 4.960 = 590.24 VA
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The Kill-A-Watt reports: 118.6 Volts 4.91 Amps 177 Watts 0.30 PF
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584 VA 59.9 Hz
Again, excellent results for a fairly complex load!!
Conclusion: Although this meter is very inexpensive and it's 0.2% claimed accuracy is hard to believe, it certainly does perform as advertised!! It is very simple to use and very accurate in all it's functions. For only $50, it is a must have!
Cheers,
Terry
No rights reserved. Copy, steal, and plagiarize at your pleasure.
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