Basic Electricity
1:21
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
02/01/05
also depends on the frequency and wave shape of the current.
Impedance is measured in Ohms, as is DC resistance.
Meter Operation
General
The classification of a meter depends on the inner workings and the
display of the meter. The inner workings of a meter may be either
electromechanical movement or electronic. The display may be
either analog or digital. Earlier instruments were constructed using
an electromechanical movement with an analog display and are
referred to as
analog meters
. These instruments have a needle that
rotates across the meter face and indicates the reading on a scale.
Today, most instruments are electronic with digital displays and are
referred to as
digital meters.
Hybrid meters that are electronic with
analog displays (electronic amplifiers driving an electromechanical
coil) are sometimes referred to as
electronic meters
(see Figure
1.14).
ANALOG
DISPLAY
ELECTROMECHANICAL
MOVEMENT
ELECTRONIC
CIRCUITRY
DIGITAL
DISPLAY
ANALOG
DISPLAY
METER
Figure 1.14 Meter Operation
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