1. Chapter 13
AC Measurements

2. 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

3. 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

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

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

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

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

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

9. 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

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

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

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

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

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

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

16. Frequency Counters (cont’d.)
Figure Block diagram of an electronic counter.

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

18. 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

19. 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