CHAPTER 4 ■ DIGITAL MULTIMETER
Overload/Fuse Protection
Almost every multimeter includes protection to prevent permanent damage to the device if too much
voltage or current is applied to the probes. UL (Underwriters Laboratory) Listing mark or CE (Conformité
Européenne) marking is a good sign (see Figure 4-5). However, be aware that despite protection on the
probe inputs, many meters are still vulnerable to damage through their transistor, capacitor, or data ports.
Figure 4-5. Underwriters Laboratory listing mark and Conformité Européenne marking
Nice-To-Have Features
Here are features that are worth paying extra for, if you can afford to do so:
Capacitance
Measured in farads, capacitance indicates the number of electrons the multimeter can store. A range of
0.000000000020 f (20 pF) to 0.01 F (10,000 mF) is desirable. Many multimeters have this feature, but the range
is usually less broad.
Diode
Measured in volts or millivolts, diode test mode indicates how much electrical pressure is required to turn
on a semiconductor. This is an important feature because it can help classify different diode types and test
and identify transistors. It can even light up LEDs. Most multimeters have this feature.
Continuity
Measured in ohms, continuity indicates whether an electrical connection exists between two points. Many
multimeters have this feature, which usually includes an audible beep so that you don’t need to look at the
display to see when something is connected.
If an audible continuity feature doesn’t exist on your multimeter, you can use the resistance setting
instead, although you’ll need to look at the display rather than listen for a beep.
Frequency
Measured in hertz, frequency indicates how many times something is occurring per second. A range of 0.1 Hz
to 50,000,000 Hz (50 MHz) is desirable (see Figure 4-6). If the meter has a frequency function, get one that
at least measures up to 45,000 Hz (45 kHz). Some multimeters have this feature, but the range is usually less
broad.