Chapter 24
Electronic Instruments
In this chapter we’ll examine a few common instruments used to analyze electronic circuits.
24.1 Ammeter.
Anammeteris used to measure electric current. To use an ammeter, you mustbreakthe circuit at the point
at which you measure the current, the insert the ammeter into the circuit (in series).
24.2 Voltmeter
Avoltmeteris used to measure the electric potential difference between two points in the circuit. To connect
a voltmeter properly, you connect the voltmeter across the two points in the circuit whose potential difference
you wish to measure (i.e. in parallel).
24.3 Ohmmeter
Anohmmeteris used to measure electrical resistance. You should not connect an ohmmeter to a live circuit;
instead, you should completely remove the component in question, and then connect it to the leads of the
ohmmeter. The ohmmeter will connect the component to its own internal power supply, and use the resulting
current to measure the resistance.
24.4 Multimeter.
A common electronic measuring device is themultimeter, which is an ammeter, voltmeter, and ohmmeter
combined into a single device. A multimeter may also include capacitance meter, inductance meter, and/or a
frequency meter.
24.5 Oscilloscope
Anoscilloscopeis an complicated-looking device, consisting of a screen, a probe, and an impressive array of
knobs and controls. The oscilloscope is essentially a device for plotting voltage vs. time. The ground wire
on the probe is connected to the circuit ground (generally theof the power supply), and the probe is then