Copyright Goodheart-Willcox Co., Inc. Chapter 10 How Electric Meters Work 177 strings of zeros and ones through a device called the analog to digital converter (A/D). The processed information is then passed on to a microprocessor, which is the central processing unit and contains all the internal functions. The microprocessor uses stored calibrated tables and Ohm’s law calculations to generate the information on the display module for the individual to read. A digital meter has many advantages: • It has higher accuracy. • It has both automatic and manual ranging. • It measures frequency and duty cycle. • It has an easy-to-read display with back lighting. • There are multiple functions built-in, including the capacitor test, diode test, audible continuity, built-in inductive clamp, inrush current, maximum and minimum value recording, and long-term recording. • It has remote access to data, such as Bluetooth, Wi-Fi, and internet. • It includes data storage. Digital meter functions are selected through a mode switch. Many meters can have additional switches for different features. This is based on the meter’s brand and specific model. See Figure 10-10. Like analog meters, digital meters use ranges to protect the meter electronic components from excessive current. Noncontact voltage DC microampere in-line current measurement Frequency or duty cycle Resistance, continuity, capacitor test, diode test AC voltage, dc voltage Select subfunctions shown in red and inrush current hold for inductive clamp. Sine wave indicates ac Indicates dc Holds displayed value (record) Temperature Mode switch selects function Manual range select Hold (record) maximum or minimum displayed values Dual display Top for inductive clamp Bottom for all other functions Goodheart-Willcox Publisher Figure 10-10. A digital multimeter’s various selection switches.