Testing Electricity Meters

[Nicky Murtagh]

I have been asked by the owner of a caravan site to go round and check all the meters onsite to make sure they are working properly. Has anybody been asked to do this before? What is the best way to test them? I was thinking to plug something in which has a big load and watch the numbers going up?has anybody any other ideas?

Cheers

 

[Lucien Nunes]

Testing a conventional induction meter requires a range of loads as specified by the manufacturer for a particular type. As mentioned above, calibration is often most important at low loads, as this is where the meter will often spend most of its time and clock up most of the total usage. You will spot gross errors with a simple test with a heater and another kWh meter, but to confirm that they are to spec is difficult to do without the proper kit. To check the calibration of a device, you need a device with an order of magnitude better accuracy.

Consider a simple test with a heater. You want the heater to be a constant load but it will vary with the square of the voltage. If the voltage fluctuates by 5% during the test, the load power will fluctuate by 10.25%. If you are just watching an ammeter and voltmeter and trying to take an average in your head, you're likely to be more in error with your 'test' instruments than the worst error permissible on the meter. If you compare to another known good kWh meter, that might itself be on the limits but shouldn't be beyond them. If the meter under test is twice as far out in the same direction you won't know about it, because it will still look just within cal.

Finally,

the ampage on clamp meter

Ampage... Clampage... Shmampage! Did you mean current?

 

[Nicky Murtagh]

Lol yes I meant current.

 

[Nicky Murtagh]

Thanks for all the replies guys.

I started the job yesterday, I just bought a meter and a heat gun. i made up a lead with a 16a caravan plug, then the meter then a single traling socket.

I turned the heat gun on, until my new meter went up by 0.05KWH and checked it against the parks meter, I found 3 faulty meters so far.

 

[Wilko]

Hi - can I ask what the difference in readings was?

 

[Nicky Murtagh]

most of them were within 0.01 kwh, but the 3 faulty ones were just not moving at all.

 

[Percyprod]

I used to have to do meter testing on disputed accounts in the days of Norweb
Used 2 is fire or consumer's cooker to give a load. Measure volts and current, then time disc for 5 minutes and multiply by 12 to give one hour equivalent. Later we had an electronic unit with ct's which did a lot of it. Not very scientific or accurate! Can't remember the accepted accuracy. Dear mestic meters were certified as accurate for 15 years I think, and had to be changed if ESMA seals were in sding (ones on the main case).

 

[static zap]

3 faulty ones were just not moving at all.

..also think possibly "Got at" ! ..