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 5.3.2.4 Contact-Operated Demand Meters. Contactors can be attached to watt-hour
meters to transmit impulses at a rate proportional to the load. These impulses operate the
demand meter to drive a pointer or pen. The indicator is reset at the end of the demand interval
by a synchronous or mechanical clock. Contact-operated demand meters have the advantage of
easier servicing than combined watt-hour meters and demand meters. Additionally, the demands
of several lines or loads can be combined through a totalizing relay to operate one demand meter,
giving total demand. Phase-shifting transformers and scale plates are available to make the
meters read the demand in kVA. The demand in kVA may be more useful in determining the
actual load in terms of equipment rating.
5.3.2.5 Printing Demand Meter. Another type of contact-operated demand meter is the
printing demand meter which records the demand for each interval by printing it on a tape
together with the time of day.
5.3.2.6 Magnetic Media Recording Meter. A variation of the printing demand meter is the
magnetic media recording meter. Kilowatt-hour (kWH) pulses and time pulses are recorded on
magnetic media. The data can later be recovered directly by computer. The major advantage of
this magnetic storage is the elimination of manual chart or tape reading and manual
5.3.3 Metering outfits. Instrument transformers for outdoor primary metering installations
are available as packaged units. The packaged units are available for single-phase and
three-phase applications.
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