WARNING - SMART meters and ENERGY meters

Brian99_2

A proper "smart meter" is properly wired in, by the ELEC. company, replacing your normal meter; and will measure the power coming through the meter, as well as extra features. I believe Npower have installed these in many houses.

But many companies are now selling DIY meters that you fix yourself, with a little clamp round a mains cable. These are can give erroneous values, because they ONLY measure the A.C. amps, and they DONT measure the A.C. voltage OR the "power factor" (the phase difference).

Some companies have the cheek to call these "smart meters" !!

There has been confusion because of this; I've seen comments on other threads, people puzzled by the readings they get with the DIY clip-on meters.

Now if you have a PLUG-IN energy monitor you CAN measure the power consumption of a kettle etc, and some of these meters are fairly accurate; the best ones will give you the volts, the amps, the power factor, the total kWh consumed, etc.

But beware... dont try altering the cables entering the house yourself !! Not safe and not legal.

Joyful

I think your heading should be Smart meters and Energy monitors. This makes it clear the latter is not a meter.

Brian99_2

Hello Joyful... A voltmeter is a meter; an ammeter is a meter, yes ?

My energy-gadget measure volts, and amps, and watts ... so... I reckon it is also a meter.

Brian99_2

On the back of my plug-in volts-amps-watts-gadget it says "Power Meter" !!! so I'm not so daft calling it a meter !! LOL

It has the logo CE which - I think - is Certification Europe ??

From Globaltronics GmbH. (Germany) bought at ALDI.

It gives consistently sensible results.

SYNERGY

Brian99 wrote: »

A proper "smart meter" is properly wired in, by the ELEC. company, replacing your normal meter; and will properly measure the power coming through the meter. I believe Npower have installed these in many houses.

But many companies are now selling DIY meters that you fix yourself, with a little clamp round a mains cable. These are VERY approximate, because they ONLY measure the A.C. amps, and they DONT measure the A.C. voltage OR the "power factor" (the phase difference).

Some companies have the cheek to call these "smart" meters... but in fact they are NOT accurate at all.

Must be a lot of confusion because of this. I've seen comments on other threads, warning people about the inaccuracy of the DIY meters.

Now if you have a PLUG-IN energy monitor you CAN measure the power consumption of a kettle etc, and some of these meters are fairly accurate; the best ones will give you the volts, the amps, the power factor, the total kWh consumed, etc.

But beware... dont try altering the cables entering the house yourself !! Not safe and not legal.

A proper "smart meter" is properly wired in, by the ELEC. company, replacing your normal meter; and will properly measure the power coming through the meter.

A properly wired in normal meter, will also properly measure the power coming through the meter. :rotfl:

grahamc2003

Brian99 wrote: »

Must be a lot of confusion because of this. .

Agreed. You seem very confused indeed.

Brian99_2

Calm down folks. Some people have missed the point.

HERE is the "Effergy" device which does a ropy calculation of watts, based on just measuring AMPS, using a wee clamp over a cable.

http://www.amazon.co.uk/Energy-Saving-Smart-Meter-Efergy/dp/B000W0434M/ref=sr_1_1?s=electronics&ie=UTF8&qid=1322051398&sr=1-1

This kind of device is VERY approximate, IGNORING the power factor (the phase) and gets worse with inductive loads. Not very smart....but they call it a "Smart meter". This is causing misunderstandings. The OWL is similar, (some sellers claim this is smart too).

---

Now here is the British Gas "Smart Meter", which has to be wired in professionally, and will measure the power correctly and has more features than your usual meter, easier to watch your consumption.

http://www.britishgas.co.uk/energy-efficiency/smart-meters.html

bondy01

Brian99 wrote: »

HERE is the "Effergy" device which does a ropy calculation of watts, based on just measuring AMPS, using a wee clamp over a cable.

This kind of device is VERY approximate, and gets worse with inductive loads. Not very smart....but they call it a "Smart meter". Beware of this kind of marketing. The OWL is similar, (but they dont claim it's smart).

I've got a Efergy usb monitor and it consistantly reads 4-5% high. I could try tweaking the default voltage on it to improve the accuracy but I don't think that is too bad.

grahamc2003

Brian99 wrote: »

Calm down folks. Some people have missed the point.

Is your point that a £600 accurated and certified professional meter used for billing and control purposes and professionally installed is more accurate than a £20 clip on device?

Is another of your points that it's not wise to tamper with the mains cable entering your house?

Really, I don't think there are many readers missing your points.

Surely your op should have been a reply to someone who was confused about the accuracy of a mains smart meter and an energy monitor - that way it would have been in context. Having said that, I haven't read any posts where anyone has that misconception.

Also, you seem to be talking about 3 devices, and not two as your title suggests (and even your title is misleading as both smart meters and energy monitors measure, directly or indirectly, the same things - energy, power and cost).

If you are saying the following about the three devices, then I'd agree with you ...

A smart meter measures very accurately and directly rms voltage, rms current and frequency, and uses algorithms to calculate power, reactive power, energy and cost.

A plug-in energy monitor/power meter measures accuaretly (but not as accuretly as above) rms voltage, rms current and frequency, and uses algorithms to calculate power, reactive power, energy and cost of devices connected to the plug

An clip on energy monitor measures inductance (at some levels reasonably accurately, but at others very inaccurately), and uses algorithms and assumptions of voltage and frequency to calculate/estimate apparent power, energy and cost. Mine measures energy usage and costs about 10% too high overall, which is sufficient accuracy to make the device useful, imv.

Brian99_2

Graham you have explained it well, except the clip-on meter does NOT measure inductance; you could say it uses inductive linking, similar to a transformer.

I have put the main point in red below, since it is getting lost in all the commotion !

espresso

Brian99 wrote: »

Calm down folks. Some people have missed the point.

Surely it is you who has missed the point and your WARNING threads are pointless! One post was sufficient on this forum, posting the same thing twice breaks the forums rules.

Who in their right mind would compare a permanently wired calibrated meter with a DIY clip on one, other than you of course.