gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
170531-2016 EDT
Some comments on the Kill-A-Watt EZ. I have made comments on this instrument in the past. So some of these comments are a repeat.
I purchased one or two of the non-EZs before the EZ became available. These were not too good in functional range, or resolution. Also had reliability problems, and the EZ also has reliability issues.
The Kill-A-Watt EZ is a low cost instrument, in the past was about $30 at Home Depot, can be very useful, and is moderately accurate. It does appear to read real power, and real RMS. Seems to perform very well on loads with a large phase shift of current. The TED power monitor systems does not do very well on large current phase shifts. It, the TED system, actually might to some extent give someone the false idea that a "Power Saver" (power factor correction capacitor in a residential application) would save energy, and reduce their bill.
Using one of my EZs with a high quality 30 ufd capacitor as the load (polyprop) I read:
123,1 V, 1.4 A, 0.7 W, 173 VA, and 1.00 PF (this is wrong, but reads correctly at near 0 on other EZ units). This particular EZ does read PF correctly (actually it is calculated by EZ) for phase shifts that are not this close to 0.
My Fluke 27 reads 123.5 when EZ reads 123.1 .
Calculated reactance of 30 ufd at 60 Hz is about 90 ohms, from this calculated current would be 1.37 A. Good check. From EZ data I calculate PF at 0.004 .
No way is an Apple cellphone charger going to to have an input power of 90 W when charging. An IBM Thinkpad is probably only 30 W when operating with the screen illumination on bright. My Samsung cellphone charger, when starting to charge, first reads about 0.05 to 0.08 A, 5.4 W, and 7 VA. Just look at the size of one of these chargers and you know it is probably less than 10 W. Very shortly, possibly a minute or so, after starting to charge the power input drops significantly.
A Kill-A-Watt in combination with a 1500 W space heater can be used to study branch circuit problems.
The thread about a bathroom light dimming resulting from a blow dryer load could be troubleshot with a Kill-A-Watt EZ.
.
Some comments on the Kill-A-Watt EZ. I have made comments on this instrument in the past. So some of these comments are a repeat.
I purchased one or two of the non-EZs before the EZ became available. These were not too good in functional range, or resolution. Also had reliability problems, and the EZ also has reliability issues.
The Kill-A-Watt EZ is a low cost instrument, in the past was about $30 at Home Depot, can be very useful, and is moderately accurate. It does appear to read real power, and real RMS. Seems to perform very well on loads with a large phase shift of current. The TED power monitor systems does not do very well on large current phase shifts. It, the TED system, actually might to some extent give someone the false idea that a "Power Saver" (power factor correction capacitor in a residential application) would save energy, and reduce their bill.
Using one of my EZs with a high quality 30 ufd capacitor as the load (polyprop) I read:
123,1 V, 1.4 A, 0.7 W, 173 VA, and 1.00 PF (this is wrong, but reads correctly at near 0 on other EZ units). This particular EZ does read PF correctly (actually it is calculated by EZ) for phase shifts that are not this close to 0.
My Fluke 27 reads 123.5 when EZ reads 123.1 .
Calculated reactance of 30 ufd at 60 Hz is about 90 ohms, from this calculated current would be 1.37 A. Good check. From EZ data I calculate PF at 0.004 .
No way is an Apple cellphone charger going to to have an input power of 90 W when charging. An IBM Thinkpad is probably only 30 W when operating with the screen illumination on bright. My Samsung cellphone charger, when starting to charge, first reads about 0.05 to 0.08 A, 5.4 W, and 7 VA. Just look at the size of one of these chargers and you know it is probably less than 10 W. Very shortly, possibly a minute or so, after starting to charge the power input drops significantly.
A Kill-A-Watt in combination with a 1500 W space heater can be used to study branch circuit problems.
The thread about a bathroom light dimming resulting from a blow dryer load could be troubleshot with a Kill-A-Watt EZ.
.
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