## Weston Frequency Meter

Definition: The Weston frequency meter is a moving iron instrument used for measuring the unknown frequency of a signal. The frequency meter consists one inductive and one resistive coil. When the frequency of the signal varies from standard frequency, the current distribution across the coils becomes changes. Working Principle of Weston Frequency Meter The Weston …

## Construction of Potential Transformer

The potential or voltage transformer is a step-down transformer used for transformation of voltage from a high value to fractional value. The measuring instrument like ammeter, voltmeter, wattmeter, etc. designs for low voltages. If the measuring apparatus connects to the high voltage lines for measurement, the devices may get burned or damage. Thus, the potential …

## Thermocouple

Definition: The thermocouple is a temperature measuring device. It uses for measuring the temperature at one particular point. In other words, it is a type of sensor used for measuring the temperature in the form of an electric current or the EMF. The thermocouple consists two wires of different metals which are welded together at …

## Low Power Factor Wattmeter

Definition: The instrument that measures the low value of power factor accurately is known as the Low Power Factor Wattmeter (LPFW). The low power factor meter is used for measuring the power of the highly inductive circuit. It is also used in the resistive circuit which has a power factor range from 0.5 to 1. …

## Vibration Galvanometer

Definition: The galvanometer in which the oscillation frequency of the moving element and the measurand current becomes equal is known as the vibration galvanometer. It uses for detecting the alternating current or alternating electromotive force. Working Principle of Vibration Galvanometer When an alternating current is passing through the moving element of the galvanometer, deflecting torque produces …

## Limiting Error

Definition: The limited deviation of the measured value from the true value is known as the limiting error or guarantee error. Such type of error is fixed on the instrument. The magnitude of the limiting error depends on the design, material and the workmanship used for the construction of the instrument. For obtaining a high degree …

## Differential Voltmeter

Definition: The voltmeter which measures the difference between the known and the unknown voltage source is known as the differential voltmeter. It works on the principle of comparison between the reference and the unknown voltage sources. The accuracy of the differential voltmeter is very high.The principle of operation of the differential voltmeter is similar to …

## Rectifier Type Instrument

Definition: The instrument which uses the rectifying element for measuring the voltage and current is known as the rectifying instruments. The rectifying element converts the alternating current to the direct current which indicates by the DC responsive meter. The PMMC uses as an indicating instrument. The sensitivity of the rectifying instruments is high as compared …

## Electrothermal Instrument

Definition: The instrument whose working depends on the heating effects of the measuring current is known as the electrothermal or electrothermic instrument. This device is used for measuring the high-frequency current. The most significant advantage of this type of instrument is that it measures the high range frequency current more than the Moving Iron and …

## Difference Between Random & Systematic Error

The most significant difference between the random and the systematic error is that the random error occurs because of the unpredictable disturbances caused by the unknown source or because of the limitation of the instrument. Whereas, the systematic error occurs because of the imperfection of the apparatus. The other differences between the random and the systematic error …