Specifications

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7. INSTRUMENTS AND TESTING
7.1 INTRODUCTION
In this modern world, use of electricity everywhere is inevitable. As almost all industrial
machines, home appliances etc. are working on electrical energy, it is must to inspect and test
the electrical energy for its quality before energizing machines/appliances. Also if the machines/
appliances are not working on giving electrical energy, it is required to carry out some test to
identify the fault. So here we will see few basic testing instruments and their use.
7.2 VOLTAGE TESTER SCREWDRIVER:
A test light, test lamp, voltage tester, or mains tester is a very simple piece of electronic test
equipment used to determine the presence or absence of an electric voltage in a piece of
equipment under test. This is shown in Fig. 7.1
Fig.7.1 - Voltage tester
The test light is simply an electric lamp connected with one or two insulated wire leads.
Often, it takes the form of a screwdriver with the lamp connected between the tip of the screwdriver
and a single lead that projects out the back of the screwdriver. By connecting the flying lead to
an earth (ground) reference and touching the screwdriver tip to various points in the circuit, the
presence or absence of voltage at each point can be determined and simple faults detected and
traced to their root cause. For low voltage work (for example, in automobiles), the lamp used is
usually a small, low-voltage incandescent light bulb. These lamps usually are designed to operate
on approximately 12 V. For line voltage (mains) work, the lamp is usually a small neon lamp
connected in series with an appropriate ballast resistor. These lamps often can operate across
a wide range of voltages from 90 V up to several hundred volts. In some cases, several separate
lamps are used with resistive voltage dividers arranged to allow additional lamps to strike as the
applied voltage rises higher; with the lamps mounted in order from lowest voltage to highest,
this minimal bar graph provides a crude indication of voltage.
7.3 CONTIUNITY TEST :
Continuity refers to being part of a complete or connected whole. In electrical applications,
when an electrical circuit is capable of conducting current, it demonstrates electrical continuity.
It is also said to be “closed,” because the circuit is complete. In the case of a light switch, for
example, the circuit is closed and capable of conducting electricity when the switch is flipped to
“on.” The user can break the electrical continuity by flipping the switch to “off,” opening the
circuit and rendering it incapable of conducting electricity. In short, by performing continuity test,
we can determine the following
i) existence of continuity in the electrical wiring circuit
ii) existence of any open circuit in the circuit
iii) existence of any short circuit in the circuit