CHAPTER 4 ■ DIGITAL MULTIMETER
If a rubber boot is available but not included with the meter, it might be best to purchase the boot at the
same time as the meter. The boot may no longer be available when the meter is discontinued.
Most multimeters have a boot available.
AC Features
Unlike DC (Direct Current) that comes from a battery, AC (Alternating Current) comes from a standard
household outlet. Because of the danger from the higher voltage and current capacity of household outlets,
this book only involves DC.
AC Voltage
Measured in volts, AC voltage indicates how much peak-to-peak pressure or force the electricity has. Every
basic multimeter has this feature.
True RMS
True RMS accurately measures average AC voltage despite disturbances and fluctuations (noise) commonly
present in household and industrial power. Many multimeters now have this feature.
AC Current
Measured in amperes, AC current indicates how many electrons are speeding back and forth per second.
Every basic multimeter has this feature.
Obtaining Hook Probe Adaptors
The standard test leads that come with most multimeters have pointed tips that are appropriate for probing
circuit boards and briefly touching wires or connectors.
Hook adaptors (see Figure 4-15) and alligator clips are available that slide over each probe and clip to
the circuit being tested, resulting in hands-free connections to jumper wires and IC pins. The hook adaptor
tends to be preferable for most low-voltage digital circuits.
Figure 4-15. Hook adaptor for standard probe