Chapter 13 AC Measurements

Objectives After completing this chapter, you will be able to: Identify the types of meters available for AC measurements Identify the types of meter movements used to make AC measurements Explain the function of an oscilloscope

Objectives (cont’d.) Identify the basic parts of an oscilloscope and explain their functions Demonstrate the proper setup of an oscilloscope Describe how to use an oscilloscope to take a measurement Explain how a counter works Identify the basic parts of a counter

Figure 13-1. Analog meter used for AC measurements.

Figure 13-2. Digital meter used for AC measurements.

AC Meters (cont’d.) Figure 13-3. Rectifiers are used to convert the AC signal to a DC level prior to applying it to the meter movement.

AC Meters (cont’d.) Figure 13-4. Iron-vane meter movements do not require the conversion of AC to DC.

AC Meters (cont’d.) Figure 13-5. A clamp-on meter operates on the principle that current flowing through a wire generates a magnetic field around the wire.

Oscilloscopes Oscilloscopes provide the following information: Frequency of a signal Duration of a signal Phase relationship between signal waveforms Shape of a signal’s waveform Amplitude of a signal

Figure 13-6. An oscilloscope is the most versatile piece of test equipment available to a technician.

Figure 13-7. Block diagram of the basic parts of an oscilloscope.

Oscilloscopes (cont’d.) Figure 13-8. Basic parts of a cathode-ray tube (CRT).

Oscilloscopes (cont’d.) Figure 13-9. Oscilloscope faceplate.

Oscilloscopes (cont’d.) Figure 13-10. Oscilloscopes vary in the number of front panel controls.

Frequency Counters Frequency counter Measures frequency by measuring a known frequency against an input frequency

Frequency Counters (cont’d.) Figure 13-12. Block diagram of an electronic counter.

Bode Plotters Bode plotter Produces a graph of a circuit’s frequency response Useful in analyzing filter circuits

Summary Types of meters for AC measurements: analog and digital Types of meter movements used to make AC measurements: moving coil, iron-vane, clamp-on An oscilloscope provides a visual display of what is occurring in the circuit

Summary (cont’d.) A counter measures frequency by comparing an unknown frequency to a known frequency A Bode plotter produces a graph of a circuit frequency response