2 - Analog meters

Abstract

This chapter focuses on the analog meters. The most common test instrument encountered in the laboratory is the analog meter, using the moving-coil movement as its display. Moving-coil movements are generally manufactured with sensitivities ranging between about 10 μA and 1 mA at full scale deflection (FSD); that is, when the pointer is deflected to the furthermost point by the current. Using mechanical switches to switch multipliers, shunts and cells in and out of circuit with a moving-coil movement, an analog meter capable of measurement of many ranges of voltage, current and resistance can be constructed. Such an instrument earns the name volt-ohm-milliammeter (VOM), although more commonly it is called a multimeter. The accuracy quoted for a multimeter is specified as a percentage of full scale deflection, which means that the accuracy is dependent on the position of the pointer on the scale for any particular measurement. Factor, which may affect the accuracy of a measurement taken with an analog meter, is the resolution with which the measurement is perceived by the user. Further, analog meters are often used to measure distortion.