Hardware Hacking Projects for Geeks

9

Introduction

After you have completed building this circuit, con-

nect a 9V battery and test it out. When you press the

button, the LED should turn on. If it doesn’t work,

don’t despair. The next section covers how to use a

multi-meter to troubleshoot your circuits.

How to use a multi-meter

A multi-meter is often called a Volt-Ohm meter

(VOM), a digital volt meter (DVM), or simply a meter.

A multi-meter measures voltage, resistance, and some-

times current. Advanced models can also measure the

value of capacitors, time, and temperature.

The multi-meter typically has two plastic sticks with

metal tips (called probes) that are attached by flexible

wires connected to two sockets in the body of the

meter. The probe wires are removable. In the center of the instrument is

a dial that selects the electrical characteristic you will be measuring. The

meter shown in Figure I-6 measures resistance, DC voltage, AC voltage,

current, diode forward voltage, and battery voltage.

The multi-meter lets you see what is going on inside an electronic circuit.

Unless you always build every circuit perfectly, you will be using a multi-

meter to find out what is wrong.

We will now use a multi-meter to measure voltage and current in the circuit

you just built.

How to measure voltage in a circuit

The multi-meter’s dial will usually have two areas marked ...