PMMC stands for Permanent Magnet Moving Coil. PMMC Instruments are the most accurate type for the measurement of DC current or voltage. Construction of PMMC Instruments Permanent Magnet Moving Coil or PMMC Instruments consists of following components: Moving Coil Magnet System Control Spring Damping Pointer and Scale 1. Moving Coil The moving coil made up … Read morePermanent Magnet Moving Coil or PMMC Instruments
Construction The construction of a single phase Electrodynamometer Power Factor Meter is shown in fig. 1. It consists of a fixed coil which acts as the current coil. This coil is split up into two parts and carries the current of the circuit under test. Therefore, the magnetic field produced by this coil is proportional to the main current. Two identical pressure coils A … Read moreSingle Phase Electrodynamometer Power Factor Meter
Functional Block diagram of Digital Frequency Meter Working principle of Digital frequency meter 1. The unknown frequency signal is fed to the Schmitt trigger. The signal may be amplified before being applied to Schmitt trigger. 2. In a Schmitt trigger, the signal is converted into a square wave with a very fast rise and fall times, … Read moreDigital Frequency Meter | Block Diagram & Working
Difference between the construction of PMMC and dynamometer instruments PMMC (Permanent moving magnet coil) Instrument (1) Moving Coil: The moving coil is wound with many turns of enamelled or silk-covered copper wire. The coil is mounted on a rectangular aluminium former which is pivoted on jewelled bearings. The coils move freely in the field of … Read morePMMC & Dynamometer Instruments Construction Difference
The phototransistor is a semiconductor light sensor formed from a basic transistor with a transparent cover that provides much better sensitivity than a photodiode. It is basically a 3-layer semiconductor device which has a light-sensitive base region. The base senses the light and converts it into the current which flows between the collector and the … Read morePhototransistor | Symbol, Operation and Applications
The measurement of a given quantity is essentially an act or result of comparison between a quantity, whose magnitude (amount) is unknown with a similar quantity whose magnitude (amount) is known, the latter being called standard. Measurement involves the use of the instrument as a physical means of determining quantities or variables. The instruments serve … Read moreMeasurement Systems | Functions & Applications
An Instrument may be defined as a device or a system which is designed to maintain a functional relationship between prescribed properties of physical variables and must include ways and means of communication to a human observer. Functional Elements of an Instrumentation System Most of the measurement system contains following main functional elements as shown … Read moreFunctional Elements of an Instrumentation System
Static Sensitivity Static Sensitivity of an instrument or an instrumentation system is defined as the ratio of the magnitude of the output signal or response to the magnitude of an input signal or the quantity being measured. The reciprocal of sensitivity is defined as inverse sensitivity or deflection factor. The sensitivity of an instrument should … Read moreStatic Sensitivity, Linearity and Hysteresis
In this article, we will see the difference between accuracy and precision terms. They are also most confusing terms in measurements regarding instruments. What is Accuracy? Accuracy is the closeness with which the instrument reading reaches the true value of the quantity being measured. 1. The accuracy of measurement means conformity to truth. 2. The … Read moreAccuracy and Precision
Scale Range and Scale Span are two most confusing terms in measurement. Many a times students get confused with these two terms. Here I have clarified both these terms in the easy language. In analog instruments, the value of measurand is indicated by the pointer on a scale. A scale has some values mentioned on … Read moreScale Range and Scale Span