CHAPTER 4 ■ DIGITAL MULTIMETERDuty Cycle
Measured in percentages, duty cycle indicates how often a measurement is high as opposed to how often
a measurement is low. This turns out to be an important measurement in robotics, as it is the key to
PWM (pulse-width modulation). Only some multimeters have this feature, which often appears in
frequency mode.
Autoranging
In the past, a user had to manually dial the meter to select the expected maximum value to be measured
(see Figure 4-7). Autoranging automatically determines the range and subsequently bumps it up or down
as necessary, so you can concentrate on the circuit. Autoranging can occassionaly be annoying if the
measurement is occurring on the border between two ranges, because the device will keep switching
between the modes unless the multimeter also has some sort of range-hold button. Most modern
multimeters have the autoranging feature, which you can easily identify by uncluttered dials (see Figure 4-8).
Nowadays, avoid manual-ranging meters.
Figure 4-6. Meter displaying 38-kHz frequency measurement