This chapter introduces you to several test instruments and components found in those test instruments. It will also serve as a review of some of the basics of electronic theory related to test equipment. You may be required to check the power consumption and the input-signal power levels of electronic equipment. The measurement of ac power is further complicated by the frequency limitations of various power meters. Because the actual calculation of decibel measurements is seldom required, the following explanation is somewhat simplified.
Most test equipment is designed to measure and indicate decibels directly.
This eliminates the need for you to perform complicated calculations. Nevertheless, a basic explanation of the decibel measurement system is necessary for you to understand the significance of dB readings and amplifier-gain ratings that are expressed in decibels. The bel is a unit that expresses the logarithmic ratio between the input and the output of any given component, circuit, or system. It may be expressed in terms of voltage, current, or power. Most often, it is used to show the ratio between input and output power to figure gain.