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CompTIA A+ Certification All-in-One Exam Guide

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Figure 7-7 Author’s ancient but reliable digital multimeter

Note that some multimeters use symbols rather than letters to describe AC

and DC settings. For example, the V with the solid line above a dashed line in

Figure 7-8 refers to direct current. The V~ stands for alternating current.

Figure 7-8 Multimeter featuring DC and AC symbols

Most multimeters offer at least four types of electrical tests: continuity,

resistance, AC voltage (VAC), and DC voltage (VDC). Continuity tests

whether electrons can flow from one end of a wire to the other end. If so, you

have continuity; if not, you don’t. You can use this setting to determine if a

fuse is good or to check for breaks in wires. If your multimeter doesn’t have a

continuity tester (many cheaper multimeters do not), you can use the

resistance tester. A broken wire or fuse will show infinite resistance, while a

good wire or fuse will show no resistance. Testing AC and DC voltages is a

matter of making sure the measured voltage is what it should be.

Try This! Using a Multimeter to Test AC Outlets

Every competent technician knows how to use a multimeter, so if you

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