2-1CHAPTER 2MISCELLANEOUS MEASUREMENTSLEARNING OBJECTIVESUpon completing this chapter, you should be able to:1.Define and explain the use of the terms "dB" and "dBm" as they apply to power measurements.2.Describe the use of resistive loads, bolometers, and thermocouples in power measurements.3.Explain the measurement of mechanical rotation using the tachometer, stroboscope, and thestrobotac.4.Explain the measurement of frequency in various ranges using vibrating reeds, tuned circuits,heterodyne frequency meters, absorption wavemeters, cavity wavemeters, and frequencycounters.5.Describe the use of frequency-measurement devices, oscilloscopes, and spectrum analyzers inwaveform analysis and maintenance.6.Describe semiconductor testing and applicable terms in maintenance.INTRODUCTIONIn chapter 1, you studied test equipment administration and the basic measurements that alltechnicians are responsible for performing. Chapter 2 presents miscellaneous measurements that are fairlycommon; keep in mind, however, that you may not routinely perform these measurements in yourparticular job. This chapter introduces you to several test instruments and components found in those testinstruments. It will also serve as a review of some of the basics of electronic theory related to testequipment.POWER MEASUREMENTSYou may be required to check the power consumption and the input-signal power levels of electronicequipment. The determination of dc power is fairly simple; recall that the unit of power, the watt, is theproduct of the potential in volts and the current in amperes (P = E I).As discussed in NEETS, Module 2, Introduction to Alternating Current and Transformers, the phaseangle of the voltage and current must be considered for accurate ac power measurements. Themeasurement of ac power is further complicated by the frequency limitations of various power meters. Ifthere is no phase angle difference, you can compute ac power in the same manner as dc power; that is, bydetermining the effective value of the product of the voltage and current.For equipments that operate in the audio-frequency (af) range, power levels have to be determined inthe performance of routine checks and during corrective maintenance procedures.