The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. Contents. 1 Electrodynamic; 2 Electronic. Dynamometer Type Wattmeter Principle: If two coils are connected such Hence an electrodynamic instrument, when connected as shown in. In electrodynamometer type wattmeter, moving coil works as pressure coil. We know that instantaneous torque in electrodynamic type instruments is directly.

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Now the reason is very obvious of using two fixed coils instead of one, so that it can be constructed to carry considerable amount of electric current. Errors may be due connections. This may not be specified in the meter’s manual. Dynamometer type wattmeter works on very simple principle and this principle can be stated as “when any electric current carrying wattmrter is placed inside a magnetic fieldit experiences a mechanical force and due this mechanical force deflection of conductor takes place”.

Electrodynamometer Type Wattmeter

A dynamometer type wattmeter essentially consists of two coils called fixed coil and moving coil. The construction of a dynamometer instrument to some extent resembles the PMMC instrument.

Unsourced material may be challenged and removed. Air friction damping is used, as eddy current damping will distort the weak operating magnetic field and thus it may leads to error. Errors may be due to mutual inductance effects. Circuit Globe All about Electrical and Electronics.

Leave a Reply Cancel reply Your email address will not be published. The deflection of the pointer of a dynamometer instrument is proportional to the current through the moving coil, but it is also proportional to the flux density of the magnetic field set up by the fixed field coils.


Limited of current flows through the moving coil so as to avoid heating. Gravity control Spring control, only spring controlled systems are used in e,ectrodynamic types of wattmeter.

Electrodynamometer Type Wattmeter | Electrical Study App by SARU TECH

You can find new Free Android Games and apps. So the expression for the torque can be written as: From Wikipedia, the free encyclopedia. Electrical typw Electricity meters Electronic test equipment.

Because the meter deflection is proportional to the field coil current and to the moving coil current. In order to derive these expressions let us consider the circuit diagram given below:. Gravity controlled system cannot be employed because there will be appreciable amount of errors. Leave a Reply Cancel reply Your email address will not be published. The resistor controls the current across the moving coil, and it is connected in series with it.

This particularly affects low power e. Related pages Measurement of Three Phase Power. In a dc circuit, the power supplied to a load can be determined by measuring the load voltage and current and multiplying them together: Electrical and electronic measuring equipment. In other projects Wikimedia Commons. The specification for the meter should specify the reading error for different situations.

Consequently, its major application is as a wattmeter. Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage.

Gravity controlled system cannot be employed because they will appreciable amount of errors. By limiting the current, the moving coil is made of light weight which in turn increases the sensitivity of the instrument.

Because fairly large currents are required to set up the necessary field flux, the dynamometer instrument is not as sensitive as a PMMC instrument. Instruments with moving coils can be calibrated for direct current or power frequency currents up to a few hundred hertz. There is uniform scale is used in these types of instrument as moving coil moves linearly over a range of 40 degrees to 50 degrees on either sides.


The pressure coil can also be tapped to change the meter’s range. The instrument whose working depends on the reaction between the magnetic field of moving and fixed coils is known as the Electrodynamo-meter Wattmeter. The instruments in which the operating field is produced by the fixed coils are known as electrodynamic or dynamometer type instruments. Please share it, your one share can change my life. The fixed coil connects in series with the circuit whose power consumption use to be measured.

Leave this field empty.

It is, therefore, called potential coil. The lowest measurable current is given as 0. The current and voltage of the fixed and moving coil generate the two magnetic fields. Let I 1 and I 2 be the instantaneous values of currents in pressure and electric current coils respectively.

Fixed Coil The fixed coil is divided into two equal parts and these are connected in series with the load, therefore the load current will flow through these coils. Arbitrary waveform generator Digital pattern generator Function generator Sweep generator Signal generator Video-signal generator. And the value of current is given by the equation.

The voltage across the pressure coil of the circuit is given as.

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