However, most instruments can be
broadly grouped under two general headings: those having analogue and
those with digital displays.
∴ I
V
R
S
T
S
V
A
12
6
2
Ω
Measuring volts and amps
The type instrument purchased for general use the electrotech-
nical industries difficult choice because there are many different
types the market and every manufacturer’s representative convinced
that his company’s product the best. However, you are an
electrician service engineer intending purchase new instrument, I
think balance that good-quality digital multimeter such that shown
in Fig.11
Digital multimeter suitable for
testing electrical and electronic
circuits.
.
Most meters using analogue scale incorporate mirror eliminate par-
allax error.
FIGURE 5. They are
the only choice when general trend variation value observed. The user must look straight the pointer the scale when tak-
ing readings and the correct position indicated when the pointer image
in the mirror hidden behind the actual pointer.11 would best. Modern digital meters use semiconductor tech-
nology give the instrument very high-input impedance, typically about
10MΩ and, therefore, they are ideal for testing most electrical electronic
circuits. Having moving parts, digital meters tend
to more rugged and, having very high-input impedance, they are ide-
ally suited testing all circuits that electrician might work his
daily work.
The choice between analogue and digital display difficult one
and must dictated specific circumstances.
Digital meters instruments
Digital meters provide the same functions analogue meters but they
display the indicated value using seven-segment LED give numerical
value the measurement. 5. Red or
danger zones can indicated industrial instruments. That the point which
a reading should taken from the appropriate scale the instrument.
Analogue meters instruments
Analogue meters have pointer moving across calibrated scale. The fuel gauge
on motor car often indicates full, half full danger analogue dis-
play which much more informative than indication the exact num-
ber litres petrol remaining the tank. 5.9, lS.
These meters are only accurate when used the calibrated position usu-
ally horizontally.
Definition
Analogue meters have pointer mov-
ing across calibrated scale.
Hi-fi equipment often uses analogue displays indicate how power lev-
els vary with time, which more informative than specific value.Basic Electrical Installation Work
110
Let call the current flowing through both resistors and R2, shown Fig.
Definition
Digital meters provide the same func-
tions analogue meters but they
display the indicated value using a
seven-segment LED give numeri-
cal value the measurement
