Power Meter

[Simmo]

Anyone know where to get locally an outlet power usage meter like this.

[jeffer]

I've looked in the past and have not been able to locate one in Thailand. I asked at Amorn and even they had no idea where to get one. I have also tried looking and asking in Singapore, no luck there either. Maybe the best idea is if you know someone who can bring in one from the USA.

[Crossy]

I've looked in the past and have not been able to locate one in Thailand. I asked at Amorn and even they had no idea where to get one. I have also tried looking and asking in Singapore, no luck there either. Maybe the best idea is if you know someone who can bring in one from the USA.

WARNING WILL ROBINSON!!!

A US one will likely go bang - 110V

[jeffer]

Fair point. I thought they must be dual voltage as I'm sure I've seen the Kill A Watt reviewed in Aussie magazines before. 

[dingdongrb]

I've never seen or heard of the meter pictured before. What is the typical cost? Why wouldn't one just buy a FLUKE DVM, as it would be more versatile and provide other uses?

[Crossy]

I've never seen or heard of the meter pictured before. What is the typical cost? Why wouldn't one just buy a FLUKE DVM, as it would be more versatile and provide other uses?

Coz the Fluke doesn't measure power, frequency (ok, some do) and power factor

UK Kill-a-Watt (230V) is 20 Quid http://www.reuk.co.uk/Buy-UK-Power-Meter.htm obviously will need adaptors for Thailand.

Edited November 24, 2008 by Crossy

[dingdongrb]

I've never seen or heard of the meter pictured before. What is the typical cost? Why wouldn't one just buy a FLUKE DVM, as it would be more versatile and provide other uses?

Coz the Fluke doesn't measure power, frequency (ok, some do) and power factor

UK Kill-a-Watt (230V) is 20 Quid http://www.reuk.co.uk/Buy-UK-Power-Meter.htm obviously will need adaptors for Thailand.

My FLUKE measures 'frequency' and for power and power factor it's merely applying some basic math, not too extremely difficult....

I guess everyone has their preference. Mine is my trusty FLUKE and before that it was my Simpson. Other than having my DVM, I used to (before moving to LOS) have my Tektronics 'lunchbox' 4 ch O'scope..... These items have got me by for the past 30+ years....

Edited November 24, 2008 by dingdongrb

[Crossy]

My FLUKE measures 'frequency' and for power and power factor it's merely applying some basic math, not too extremely difficult....

Please explain how you measure power factor with just a DMM, I'm intrigued

Even if the PF is unity, measuring power requires inserting the ammeter into one of the lines (unless you have a clamp which will likely cost more than the Kill-a-Watt), a somewhat hazardous practice for the non technical which becomes even more fun when you forget to put the meter back on 'Volts' (a t-shirt of which I am a less than proud owner).

20 Quids worth of gadget does all the hard work and in total safety

Edited November 24, 2008 by Crossy

[stumonster]

which becomes even more fun when you forget to put the meter back on 'Volts' (a t-shirt of which I am a less than proud owner).

if your normal realm is 4-20mA you learn that one very quickly

20 Quids worth of gadget does all the hard work and in total safety

they must be around - and guaranteed they are made in chine - check alibaba.com for a manuf and proceed from there

[Simmo]

Yes I know you can do the same thing with a good multimeter, but who wants to be messing around with mains wiring when this is much easier.

[Crossy]

Yes I know you can do the same thing with a good multimeter, but who wants to be messing around with mains wiring when this is much easier.

That's two of you now!

I wish someone would tell me how to measure power factor with a regular multimeter

Agreed on the safety front, and the Kill-a-Watt is just so much more convenient.

[dingdongrb]

My FLUKE measures 'frequency' and for power and power factor it's merely applying some basic math, not too extremely difficult....

Please explain how you measure power factor with just a DMM, I'm intrigued

Even if the PF is unity, measuring power requires inserting the ammeter into one of the lines (unless you have a clamp which will likely cost more than the Kill-a-Watt), a somewhat hazardous practice for the non technical which becomes even more fun when you forget to put the meter back on 'Volts' (a t-shirt of which I am a less than proud owner).

20 Quids worth of gadget does all the hard work and in total safety

Do I really have to explain basic electronics to you? I will if you are wanting to learn that bad...... But first let me ask these basic questions, how often do you want to really measure the PF? And how does this help you?

[Crossy]

Do I really have to explain basic electronics to you? I will if you are wanting to learn that bad...... But first let me ask these basic questions, how often do you want to really measure the PF? And how does this help you?

NO you don't have to explain basic power calculations to me (my degree is in Electrical and Electronic Engineering), I want you to tell me how YOU measure real power (or power factor) using just a multimeter.

Simply multiplying Volts by Amps gives 'apparent power' (in VA). Power factor as your illustration shows = real power (Watts) / apparent power (VA). You've still not illustrated how to measure real power (which requires a measurement of the phase angle between V and I waveforms, the PF is the Cosine of this angle).

Power factor is important, not necessarily at a domestic level, but certainly at a distribution level. Poor (low) power factor causes greater I²R losses in the distribution system and requires oversized cables and transformers.

For example a purely capacitive or inductive load can have a significant VA but ZERO power so the supplier would not be able to charge for any electricity even though their cables and transformers were at maximum capacity. Obviously an extreme example, but even running at a relatively good PF of 0.9 effectively 'wastes' 10% of your generating and transmission capacity.

You're not likely to want to measure PF, you ARE likely to want to measure real power, as it's this which your electricity meter measures (and what the leccy company bills you for). Ever noticed that UPSs, gensets and the like have ratings in Watts (real power) and VA (apparent power) which are not the same.

Edited November 25, 2008 by Crossy

[dingdongrb]

Do I really have to explain basic electronics to you? I will if you are wanting to learn that bad...... But first let me ask these basic questions, how often do you want to really measure the PF? And how does this help you?

NO you don't have to explain basic power calculations to me (my degree is in Electrical and Electronic Engineering), I want you to tell me how YOU measure real power (or power factor) using just a multimeter.

Simply multiplying Volts by Amps gives 'apparent power' (in VA). Power factor as your illustration shows = real power / apparent power. You've still not illustrated how to measure real power (which requires a measurement of the phase angle between V and I waveforms, the PF is the Cosine of this angle).

Power factor is important, not necessarily at a domestic level, but certainly at a distribution level. Poor (low) power factor causes greater I²R losses in the distribution system and requires oversized cables and transformers.

For example a purely capacitive or inductive load can have a significant VA but ZERO power so the supplier would not be able to charge for any electricity even though their cables and transformers were at maximum capacity. Obviously an extreme example, but even running at a relatively good PF of 0.9 effectively 'wastes' 10% of your generating and transmission capacity.

You're not likely to want to measure PF, you ARE likely to want to measure real power, as it's this which your electricity meter measures (and what the leccy company bills you for). Ever noticed that UPSs, gensets and the like have ratings in Watts (real power) and VA (apparent power) which are not the same.

See Crossy, you just answered my very first concern and perhaps some of your own concern, with me it was why would the average homeowner want/need to measure the power factor. You replied that it's more for power distribution work. So wouldn't someone in the line of this type of work needing to measure power factor have equipment more suitable than this 'Kill-A-Watt' gizmo? And yes there is much safety to be concerned about when working around high voltage power lines.

Measure 'real' power = Voltage measured (a DVM will do this) times the current (again a DVM will do this). Do I need to? NO!!!! Do I want to? WHY??? Can I? YES

NOTE: Always good to see someone else in the same field. Although I have never done any professional work on high voltage power distribution lines (other than wiring my house in the USA) I have worked with high power power supplies (120A 600V) as well as high voltage supplies (6kV 300mA) - Both DC and RF

[Crossy]

Measure 'real' power = Voltage measured (a DVM will do this) times the current (again a DVM will do this). Do I need to? NO!!!! Do I want to? WHY??? Can I? YES

Agreed, nice to fine someone who has at least an inkling of what's going on

Sorry mate, Voltage x Current = Apparent Power (in VA).

To measure Real Power (in Watts) you need to take into account the phase angle which a Wattmeter does.

When I were a lad a Wattmeter was a wonderful moving coil meter in a mahogany case which was treated with the reverence it deserved, needed connections for voltage and current. It was quite easy to fry one on an inductive load as there were loads of Amps but the meter read zero (or close to it). The Machines and Control lecturer at Bath Uni. a certain Mr Bentley (Fray Bentos) would jump around like a cat on a hot tin roof if he saw a Wattmeter in circuit without a series ammeter to 'remind' you that lots of Amps were actually flowing.

I think the idea of the Kill-a-Watt is to allow the average Joe to easily and safely measure 'vampire' loads and see just how much juice he's wasting by leaving kit on standby rather than 'off'.

Edited November 25, 2008 by Crossy

[dingdongrb]

Measure 'real' power = Voltage measured (a DVM will do this) times the current (again a DVM will do this). Do I need to? NO!!!! Do I want to? WHY??? Can I? YES

Agreed, nice to fine someone who has at least an inkling of what's going on

Sorry mate, Voltage x Current = Apparent Power (in VA).

To measure Real Power (in Watts) you need to take into account the phase angle which a Wattmeter does.

When I were a lad a Wattmeter was a wonderful moving coil meter in a mahogany case which was treated with the reverence it deserved, needed connections for voltage and current. It was quite easy to fry one on an inductive load as there were loads of Amps but the meter read zero (or close to it). The Machines and Control lecturer at Bath Uni. a certain Mr Bentley (Fray Bentos) would jump around like a cat on a hot tin roof if he saw a Wattmeter in circuit without a series ammeter to 'remind' you that lots of Amps were actually flowing.

I think the idea of the Kill-a-Watt is to allow the average Joe to easily and safely measure 'vampire' loads and see just how much juice he's wasting by leaving kit on standby rather than 'off'.

Agreed on everything you have said... I just thought it was amusing that the 'average Joe' would even been inclined to see how much power his refrigerator was using and only be concerned if his beer was cold or not........

I find these newer technological power meters to be much more modern than the older 'moving coil' ones.....

Edited November 25, 2008 by dingdongrb

[Crossy]

I find these newer technological power meters to be much more modern than the older 'moving coil' ones.....

Nah Mate, THIS is a Wattmeter

Be quick and it can be yours too http://cgi.ebay.com/Rare-Antique-GE-Polyph...%3A1|240%3A1318 and at a current bid of 10 Bucks, cheaper than a Kill-a-Watt

Edited November 25, 2008 by Crossy