HOW TO READ WATT HOUR (ELECTRICITY) METER – THE IMPORTANCE OF CORRECT READING

Note: This article is specific for Electromechanical Meter Types.

There are three styles of mechanical kilowatthour meter register types in general use. One has individual dial circles as shown below:

Conventional Five-Pointer Kilowatthour Dial.

Another has interlocking dial circles as shown below:

Conventional Four-Pointer Kilowatthour Dial with Overlapping Circles.

The third style of register uses cyclometer-type dials.

Registers with dial circles have either four or five dials; five dials being provided to avoid a dial multiplier of 10 and the possibility of a register “turn-over” during the normal billing period.

Adjacent pointers rotate in opposite directions and are geared for travel so that the pointer on the right will make one complete revolution while the one next to it on the left makes one-tenth of a revolution.

When a pointer is between two figures, the smaller figure is the one to use for the reading. A watthour meter is read from right to left by reading all dials and recording the reading on a meter reading form in this same sequence.

The reason for reading the dials from right to left is that the right-hand dial governs the one to its left in each instance. With all pointers at zero and a dial multiplier of one, one clockwise revolution of the unit’s dial pointer will indicate a reading of 10 kilowatthours on the register.

A complete counterclockwise revolution of the 10’s dial pointer will indicate a reading of 100 kilowatthours on the register and so on. When reading the dials the procedure is analogous to reading 1s, 10s, 100s, and 1,000s.

Remember that each pointer must complete a revolution to advance the pointer located to its left by one division. Therefore, to correctly determine the reading of a pointer, the previous pointer (located to the right) must be consulted.

Unless this pointer has completed a revolution by reaching or passing the 0, the pointer in question has not completed the division on which it may appear to rest. For this reason, reading the meter from right to left increases both accuracy and efficiency.

A simple analogy can be made to a wristwatch. When the hour hand is near 8 and the minute hand is at 11, it is not yet 8 o’clock, but it is 7:55 and, obviously, it will not be 8 o’clock until the minute hand has advanced to 12.

Figures 17-3 and 17-4 show examples of typical watthour meter readings. To obtain the use in kilowatthours over a designated period of time, it is necessary to subtract the previous reading from the present reading.

When the dial multiplier is one, the difference will be the number of kilowatthours consumed between the two readings. When the dial multiplier is a number other than one, the difference between the readings must be multiplied by the given dial multiplier to obtain the kilowatthours consumed.

Dial multipliers of one generally are not shown, but those other than one are shown on the dial faces. Double- or two-rate registers employ two sets of dials and two complete register mechanisms that are automatically switched into gear with the moving element shaft at predetermined times. These two-rate registers are generally used in conjunction with off-peak water-heating rates.