Kill A Watt = Hunk of junk?

[Demon-Xanth]

The Kill-a-watt is probably accurate enough for most people.

...that said, you can find some nice equipment cheap because it looks old. Like my Fluke 8062 that I got for $20 (retail at the time was $460). 4.5 digits and 0.05% baby! Newer style, but lower end meters were going for quite a bit more.

 

[kranky]

Waiting for Rubycon to comment...

 

[BlahBlahYouToo]

Vdroop or Vdrop?

vdroop. do the pencil mod on the KAW. that should fix it.

 

[edro]

I have never tested my Kill-A Watt against my Fluke 87, but I know that my oil filled 800W heater was almost dead on when I put my Kill-A-Watt on it.

 

[FoBoT]

kill a watt is NOT a high accuracy test equipment
it is consumer grade, so the accuracy is going to be relatively poor

it is to give consumers a general idea of what power home appliances use, not accurate test grade results

 

[Muse]

The Kill-a-watt is probably accurate enough for most people.

...that said, you can find some nice equipment cheap because it looks old. Like my Fluke 8062 that I got for $20 (retail at the time was $460). 4.5 digits and 0.05% baby! Newer style, but lower end meters were going for quite a bit more.

Where did you find that deal?

 

[Muse]

kill a watt is NOT a high accuracy test equipment
it is consumer grade, so the accuracy is going to be relatively poor

it is to give consumers a general idea of what power home appliances use, not accurate test grade results

My impression from what I'm seeing is +/- 25% (Maybe close to accurate sometimes, maybe 25% low other times) or so, and under 15 watts, what you see may be off by a factor of 3 or more.

 

[Demon-Xanth]

Where did you find that deal?

A guy that stuffed prototype boards was closing up shop. What's funny is that I got a $100 Fluke for my dad, but paid $50 for it.


...if you don't mind a missing battery cover, here's one for $40:
http://cgi.ebay.com/FLUKE-8062A-TRU...emQQptZLH_DefaultDomain_0?hash=item3a53b8e7e3

 

[frostedflakes]

My impression from what I'm seeing is +/- 25% (Maybe close to accurate sometimes, maybe 25% low other times) or so, and under 15 watts, what you see may be off by a factor of 3 or more.

Again, as myself and others have stated before, your multimeter and Kill-a-Watt are measuring two different things.

http://en.wikipedia.org/wiki/Apparent_power#Real.2C_reactive.2C_and_apparent_power

The Kill-a-Watt can read out volt-amps as well. Set it to show that instead of watts and it should give you a number much closer to what you get by measuring voltage and current with a multimeter.

 

[Muse]

Again, as myself and others have stated before, your multimeter and Kill-a-Watt are measuring two different things.

http://en.wikipedia.org/wiki/Apparent_power#Real.2C_reactive.2C_and_apparent_power

The Kill-a-Watt can read out volt-amps as well. Set it to show that instead of watts and it should give you a number much closer to what you get by measuring voltage and current with a multimeter.

That's quite an article at Wikipedia! Well, then, for all I know, the KAW is giving me a more accurate assessment of where my utility bill is going with my devices. I just don't know. I'm going to edit the title for the thread and trail it with "?"

 

[frostedflakes]

Well like I said, Kill-a-Watt is pretty cheap as far as wattmeters go, it's far from perfect. +/-25% is way off, though, it isn't nearly that bad for most loads.

http://forums.anandtech.com/showthread.php?t=137169

 

[Muse]

Well like I said, Kill-a-Watt is pretty cheap as far as wattmeters go, it's far from perfect. +/-25% is way off, though, it isn't nearly that bad for most loads.

http://forums.anandtech.com/showthread.php?t=137169

Nice link, thanks!

 

[Rubycon]

It's not a piece of junk at all. It does exactly what it's designed to do within its price range.

What the OP is doing is measuring VA NOT Watts. If you were in the realm of direct current that would be perfectly acceptable.

If you want to analyze your power properly you need a Dranetz Visa. They cost more than your computer too!

Comparing the K-A-W to a Dranetz is like comparing the signal from a cable modem status page (http://192.168.100.1) to what a real line signal analyzer shows.

The KAW is affordable and fun. If no such device was made nobody would have a clue as to watt's going on. (sorry for the pun!)

 

[Eli]

I have 4 of them, and will never give them up. It's better than not having a clue.

 

[Jeff7]

The KAW is affordable and fun. If no such device was made nobody would have a clue as to watt's going on. (sorry for the pun!)

No, you're not.

 

[Tiamat]

For a Kill-A-Watt, its probably within +/- 10%. I wouldn't think it was any better than that.

 

[0roo0roo]

For a Kill-A-Watt, its probably within +/- 10%. I wouldn't think it was any better than that.

but wheres the proof.

 

[The Stigenator]

but wheres the proof.

ummm.. I am willing to put your KAW against my Watts up Pro which is more expensive and is rated at 1.5% accuracy.

 

[Muse]

ummm.. I am willing to put your KAW against my Watts up Pro which is more expensive and is rated at 1.5% accuracy.

OK, we need somebody to run a comparison. Surely, somebody has done this somewhere!

 

[Demon-Xanth]

OK, we need somebody to run a comparison. Surely, somebody has done this somewhere!

http://www.jonnyguru.com/forums/showthread.php?t=2695

 

[Red Squirrel]

Actually are incad light bulbs exactly the wattage they state they are? ex: is a 100w bulb exactly 100w? Or do they vary? That would probably be a good test subject for accuracy.

 

[Modelworks]

Actually are incad light bulbs exactly the wattage they state they are? ex: is a 100w bulb exactly 100w? Or do they vary? That would probably be a good test subject for accuracy.

The wattage is for the voltage labeled on the bulb, change the voltage and you change the wattage since light bulbs basically act like resistors. They make great loads for testing power supplies. A lot of bulbs are rated 110V while many homes are 125V so that 100W bulb is using more than 100W

 

[Rubycon]

The wattage is for the voltage labeled on the bulb, change the voltage and you change the wattage since light bulbs basically act like resistors. They make great loads for testing power supplies. A lot of bulbs are rated 110V while many homes are 125V so that 100W bulb is using more than 100W

Another tactic is to make the operating voltage 130VAC and label them long life! :biggrin:

Incandescent lamps make good speaker protectors for high frequency sections. This is because cold wolfram is like a dead short. Its resistance ramps up nicely as the forward current increases. In case of heavy overload the lamp glows and sinks heat that would normally be frying the voice coils (boiling ferrofluid!) or leading to power compression (and still possibly damaging the former).

Light bulb extender buttons as they were called were nothing more than thermistors that "soft started" the bulb easing up on the inrush current and sudden spike in temperature. This causes shock and is the leading cause of blowouts when the lights are turned on. With ganged lighting the inrush can blow fuses and/or trip circuit breakers that are not "tungsten rated". Ditto for photoelectric switches.

 

[Jeff7]

Light bulb extender buttons as they were called were nothing more than thermistors that "soft started" the bulb easing up on the inrush current and sudden spike in temperature. This causes shock and is the leading cause of blowouts when the lights are turned on. With ganged lighting the inrush can blow fuses and/or trip circuit breakers that are not "tungsten rated". Ditto for photoelectric switches.

Hm.....does this inrush current thing also hold true for things like 1500W electric heater elements?

 

[Rubycon]

Hm.....does this inrush current thing also hold true for things like 1500W electric heater elements?

Nope. Nichrome has a high cold resistance.