Ammeter Shunt is used for the measurement of heavy current using an Ammeter. Ammeter Shunt is basically a low resistance connected in parallel with the moving coil so that most of the current is bypassed by the Shunt and hence only a small current flows through the moving coil. Why do we need Ammeter Shunt … Read more Ammeter Shunt –Construction and Calculation
A PMMC Instrument can be used as voltmeter by just connecting a series resistance with the moving coil. This series resistance is called Voltmeter Multiplier. This combination of moving coil and multiplier is connected across the point whose voltage is to be measured. There are two main functions of voltmeter multiplier: 1) It limits the … Read more Voltmeter Multiplier – Construction and Calculation
Moving Iron Instruments are the most common type of ammeter and voltmeter used at power frequencies in laboratories. These instruments are very accurate, cheap and rugged as compared to other AC instruments. Working Principle of Moving Iron Instruments: In Moving Iron Instruments, a plate or van of soft iron or of high permeability steel forms … Read more Working Principle of Moving Iron Instruments
The deflection of needle of moving iron instrument is given in terms of rms value of voltage or current. As the angular deflection of Moving Iron Instrument is proportional to square of operating current, therefore the instrument has basically square law response. Due to this square law response, the Moving Iron Instrument Scale is non-uniform. … Read more Why Moving Iron Instrument Scale is Non-uniform?
It is a well known fact that Ammeter is always connected in series with the element through which current is to be measured. Figure below shows two cases, in one case ammeter connected in series while in other case, ammeter is connected in parallel. As an Ammeter has very low internal resistance therefore ammeter connected … Read more What Happens if Ammeter Connected in Parallel and Voltmeter Connected in Series?
A Residual Voltage Transformer is used to measure the residual voltage of three phase system during single phase fault. During normal operating condition, the summation of three phase voltage is zero but in case of single phase fault, the scenario changes and there exists a residual voltage. Let us first discuss residual voltage in case … Read more Working Principle of Residual Voltage Transformer
Permanent Magnet Moving Coil or PMMC Instruments are the best for the measurement of DC quantities like voltage and current from accuracy point of view. But there are various factors due to which error in PMMC Instrument reading may develop. To investigate the main sources of errors, let us have a look at the deflection … Read more Various Error in PMMC Instrument
Permanent Magnet Moving Coil or PMMC Instruments are the most accurate type for the measurement of DC current or voltage. The working principle of PMMC instruments are same as that of d’Arsonaval type of Galvanometer, difference being that a direct reading instrument is provided with pointer and scale. Construction of PMMC Instruments Permanent Magnet Moving … Read more PMMC Instruments – Construction and Working Principle
The current sensitivity of voltmeter of moving coil type like PMMC voltmeter is defined as the deflection per unit current in the coil. If Ɵ be the angular deflecting of needle of voltmeter for current I through the moving coil, then sensitivity of voltmeter is given as S = Ɵ / I You might think … Read more Sensitivity of PMMC Voltmeter
Electrodynamic type instrument is used for the measurement of AC and DC quantities unlike PMMC instrument which can only be used for the measurement of DC quantity. This type of instrument is known as Elctrodynamometer type instrument. Construction of Electrodynamic Type Instrument An electrodynamic type instrument consists of Two Fixed Coil, a Moving Coil, Control … Read more Electrodynamic Type Instrument – Construction and Working Principle