Phase meters (phase testers, phase rotation meters) check the
phase sequence and phase orientation in three-phase electrical
systems. They are used for energy measurements, and the monitor
the quality of audio and video transmissions. Correct phase
matching is also important in energy metering applications since
phase mismatches between channels may cause significant
measurement errors at low power factors. Bandwidth, sampling
rate, maximum channels, and operating temperature are important
parameters to specify when selecting phase meters. Bandwidth is
the frequency range over which current or voltage is measured.
Sampling rate is the frequency that a digital meter tests an
analog signal and converts to a digital value.   General
specifications for phase meters, phase testers and phase
rotation meters include display type and form factor. There are
two choices for display type: analog and digital. Form factors
are listed as bench or free-standing, clamp meter, rack-mounted,
handheld, or computer compounds. Be