IT is only of recent years that the question of the metering of electric supply has been seriously tackled. The question itself is a most difficult one, and the introduction of tariffs and the theory of statistics, and attempting ari impossible accuracy, have certainly not made it easier. The easiest way is to put a sub-standard wattmeter in series with the consumer's meter for a day or a fortnight and then read them both simultaneously. If they both read the same then everyone is satisfied. But the meter reader who has had his own sub-standard meter tested at a standardizing institution and knows the curve of error of his own meter sometimes wonders whether it is correct or not. The present limits for oconsumers' meters as described in the Electricity Supply (Meters) Act of 1936 are 2-1 per cent plus or 3J per cent minus. That is, the permissible error when the meter is going fast is less than when it is going slow. The test of the meter at no load should always be taken, and if it is rotating then it is a long and costly business to find out what is wrong.
Electricity Meters and Meter Testing
By G. W. Stubbings. (Monographs on Electrical Engineering, Vol. 6.) Pp. x + 216. (London: Chapman & Hall, Ltd., 1939.) 12s. 6d. net.