Page 274 - Electromechanical Devices and Components Illustrated Sourcebook

236 Electromechanical Devices & Components Illustrated Sourcebook

150 300 450
150 300 450 600
600
AMPERES Voltmeter
AMPERES Voltmeter
− +
− +

Main Terminals
Meter Main
Connection Terminals
600 AMP

Meter Terminals Primary Cable
Primary Cable Label
Insulating Base Measured Length
of Cable
Figure 13-43 Commercial Current Shunt
Figure 13-45 Cable Shunt

A shunt may be constructed using a copper buss bar, as technique, which verifies the electrical soundness of a con-
shown in Figure 13-44. A voltage drop over the spacing of the ductor. Continuity testing is also used extensively to trace and
meter terminals is calculated in reference to the resistance of diagnose circuits.
the copper buss bar and an appropriate meter is selected. This Figure 13-46 shows two common commercial continuity
type of shunt is often used for extremely high-current appli- testers. The combination flashlight and continuity tester is a
cations. popular tool among industrial service technicians. The basic
A measured length of cable can also act as a current shunt. tester is a very handy device when working in cramped envi-
Figure 13-45 shows a piece of coiled cable acting as a shunt. ronments. In both of these units, a battery is connected to a
Like the buss bar shunt, this arrangement is generally reserved light bulb and a pair of test leads. When the test leads are
for extremely high-current applications. touched together, the lamp turns on.

Continuity Testers

Continuity testing is probably the most common test conducted 1/4-inch Phone Jack
on electrical and electronic equipment. It is an indispensable 1/4-inch Phone Plug

Test Lead
Combination Flash Light and Continuity Tester

Alligator Clips
150 300 450 600
AMPERES Voltmeter Lamp Housing Battery Compartment

Probe

Alligator Clip Test Lead
− +
Basic Continuity Tester
Figure 13-46 Continuity Testers

A basic continuity tester can be easily built by mounting a
lamp base and battery holder onto a baseboard, as shown in
Figure 13-47. The test leads are connected with banana plugs
Copper Bar Meter Terminals and combination binding posts. This provides for the use of
Main Terminals the finished instrument in semipermanent applications on the
Figure 13-44 Buss Bar Shunt bench.