Introductory Electrical Engineering With Math Explained in Accessible Language

31Instrumentation and Bench: A Brief Introduction

31.1 Introduction

In this chapter, we introduce the reader to instrumentation, a bench equipment, essential to those willing to project and build electronic circuits.

31.2 Multimeter

A multimeter is a test tool used to measure multiple electrical values, principally voltage (Volts), current (Amperes), and resistance (Ohms).

Modern multimeters generally group a lot more functions, and some models can measure frequency (Hertz), capacitance (Farads), and inductance (Henries) and perform tests on diodes and transistors.

Modern multimeters are digital devices, like the one shown in Figure 31.1, but, in the past, they were analog needle‐based mechanical devices.

Figure 31.1 Digital multimeter.

Multimeters are formed by three basic parts:

• Display (A), where measurement readouts can be viewed.
• Dial or rotary switch (B) for selecting primary measurement values (voltage, current, frequency, etc.).
• Input jacks (C), where the test leads are inserted.

31.2.1 True RMS Multimeter

Measuring AC currents and voltages can be a problem if a multimeter is not prepared to do that.

An average responding multimeter uses average mathematical formulas to measure pure sinusoidal waves with a certain accuracy. If the wave being measured is not sinusoidal, like a square or triangular wave, the measurement accuracy decreases immensely. In many cases, ...