Page 395 - Robot Builder's Bonanza

364 BUILDING ROBOT ELECTRONICS— THE BASICS

Figure 30- 1 A digital multimeter
checks resistance, voltage, and current.
This model also performs simple checks
of a number of common electronic
components, including capacitors, diodes,
and transistors.

There are many multimeters on the market today. A meter of intermediate features and
quality is more than adequate. Meters are available at RadioShack and most online electronics
outlets. Shop around and compare features and prices.

Digital or Analog
There are two general types of multimeters available today: digital and analog. The difference
is not in the kinds of circuits they test, but in how they display the results. Digital multimeters,
which are now the most common, use a numeric display not unlike a digital clock. Analog
meters use the more old- fashioned— but still useful— mechanical movement with a needle that
points to a set of graduated scales.

Automatic or Manual Ranging
Many multimeters require you to select the range before it can make an accurate
measurement. For example, if you are measuring the voltage of a 9- volt battery,
you set the range to the setting closest to, but above, 9 volts. With most meters it
is the 20- or 50- volt range. Because you need to select the range, there are lots of
options on the dial, but in reality these options are really just variations on a theme.
The meter is easier to use than it looks.
Autoranging meters don’t require you to do this, so they are inherently quicker
to use. When you want to measure voltage, for example, you set the meter to volts
(either AC or DC) and take the reading. The meter displays the results in the read-
out panel.

G For the sake of completeness, the examples in this book that explain how to use a meter assume
you have a manual (nonautomatic) ranging model. If yours has automatic ranging, then just
skip the step that says to dial in the upper range of your expected measurement.

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