Aldi

[Mike Clarke]

[snip re: 7 quid power meter from Aldi]

Aldi still had these on offer this week in Kendal. It claimed on the pack that it displayed power factor so I bought one to "play" with. It certainly does more than they say in the brief advert but I'm not so sure how accurate it is for small loads. FWIW here's my opinions after giving it a bit of use.

It displays the power factor and the power (both instantaneous watts and cumulative KWh), plus voltage, current and frequency. For those who don't want to do simple arithmetic it can be programmed with the price per KWH and displays the total cost along with elapsed time "on load". A neat little extra is that you can set up 2 different prices for different periods of the day which may be of use for those on economy 7 tariff.

It also indicates maximum current and power, which AFAICS can only be reset by removing the batteries (2 off AG-13 button cells).

There's a facility to set an arbitrary "overload" power level which causes a red LED to light up if it's exceeded, I can't see any real use for this but I suppose it might appeal to some. Nor can I see the point of displaying the frequency, I expect the mains frequency is regulated to much closer tolerances than the accuracy of this meter.

The claimed accuracy leaves something to be desired. Voltage and current are

+/-3% but power is +/-5% of displayed value and/or +/-10 watts so not much use for checking the low power consumption of things like TV's on standby. I checked it against known resistive loads like tungsten lamps and 3KW heaters with reasonable results, it displayed the right values for a 20w halogen lamp and an 11W CFL but a 7W CFL came up as zero watts! Inductive loads like the freezer and dishwasher motor were quite erratic, in particular the value for the dishwasher swung erratically from about 120W down to near zero with corresponding power factor swinging between 0.9 and near zero.

Would I recommend one? As a serious measurement tool - no, but as a cheap and cheerful indicator it's probably OK. It's main use for me was to assess the overall consumption of things with a variable duty cycle like the freezer, or the washing machine and dishwasher where it's hard to estimate just how long the heater is no for each cycle. For most other devices just looking at the rating plate or counting the revolutions or flashes on the 'leccy board meter is probably the best approach.

[John Rumm]

Maximum current including reactive components or not?

Thanks for that Mike, it gives a much more useful indication of what you can expect than the Aldi write up!

Based on your description I would say the Maplin one probably has the edge - in that it seems to handle inductive loads like fridges etc quite well. Still not accurate on very low powers or low power factors, although it does give a steady reading.

[Mike Clarke]

Yes, it can display maximum current but no breakdown into components.

[Skipweasel]

Reset by holding in one of the buttons for three secs - but for the life of me I can't remember which.

[Mike Clarke]

Yes, it turns out that press and hold the down arrow clears the maximum values though I can't find it anywhere in the instructions. It only seems to mention press and hold "price" to clear the accumulated costs.

[Dave]

A couple of years ago, when I had the site supervisors job at the local primary school a totally deaf electrician came with a clamp meter to measure which phase to connect the new air conditioning to.

Air con lads cam down. Fitted the units and wired it up to the nearest available phase. So like you, I can't see what use they are :-)

Dave