Moving iron instruments principle, operation and type, theory. Mcq on measuring instruments 1 how engineering works. Electrodynamometer instruments are widely used as an ammeter, voltmeter and wattmeter. Movingcoil instruments there are two types of such instruments i permanent magnet type which can be used for d. Moving coil instruments there are two types of moving coil instruments namely, permanent magnet moving coil type which can only be used for direct current, voltage measurements and the dynamometer type which can be used on either direct or alternating current, voltage measurements. It works on the principle that the force acting on the coil places between the magnetic field of the permanent magnet. A dynamometer type wattmeter responds to the a average value of the active power. Pmmc instrument working principle permanent magnet moving. Hi friends, in this article, i am discussing the dynamometer type wattmeter working principle and related information, if you are interested in it then you at the right place. Moving coil, moving iron and dynamometer type instruments. Jun 08, 2019 construction and working principle of electrodynamometer type wattmeter.
It essentially consists of two coils, namely fixed coil and moving coil. Sep 12, 2019 the basic working principle of a dynamometer type instrument is somewhat similar to that of a permanent magnet moving coil instrument. This is because the resistance of moving coil is small. Sketch and explain the working of moving coil instrument. But in these instruments, the operating field is produced by the fixed coil instead of a permanent magnet.
Electro dynamometer type free download as word doc. In this post we will be discussing the torque equation in. A permanent magnet moving coil pmmc is one such instrument which is. As the moving coil is operated in a comparatively weak field, this type of instrument is. Study of the operation of moving coil type, moving iron type and dynamometer type instruments apparatus required. Pdf eec 126 instrumentation theory farouq osuolale.
Apr 24, 2018 an electrodynamic type instrument consists of two fixed coil, a moving coil, control spring, damping device and magnetic shielding arrangement. The only difference is that here instead of using permanent magnet we use a current carrying coil for producing the operating magnetic field. Electrodynamometer type wattmeter construction and working. An electrodynamic type instrument consists of two fixed coil, a moving coil, control spring, damping device and magnetic shielding arrangement. Disadvantages are due to friction at the bearings and temperature variations, errors are likely to be presentand the observed readings are may not be accurate and fresh. In a moving coil instrument, the damping torque is developed.
The basic working principle of a dynamometer type instrument is somewhat similar to that of a permanent magnet moving coil instrument. Air friction damping is provided in such instruments. Electrodynamometer meter movements use stationary coil and moving coils to develop interacting magnetic fields. Moving coil moving coil moves the pointer with the help of spring control instrument.
A induction type instrument, b dynamometer type instrument, c permanent magnet moving coil type ammeter, d thermocouple type instrument, e, leave your comments or download. The coil is mounted on a rectangular aluminium former which is pivoted on jewelled bearings. A dynamometer type instrument as shown in fig essentially consists of a fixed coil and a moving coil. An attraction type of moving iron instrument is shown diagrammatically in figure. They are used as wattmeters,varmeters and with some modification as power factor meters and frequency meters. There are two types of moving coil instruments namely, permanent magnet. Electrodynamometer type instruments construction and. Dymamometer type moving coil instruments are provided with. Moving iron instruments principle, operation and type.
Moving coil instruments 39018 there are two types of moving coil instruments namely, permanent magnet moving coil type which can only be used for direct current, voltage measurements and the dynamometer type which can be used on either direct or alternating current, voltage measurements. Permanent magnet moving coil mechanism pmmc mathematical. In electrodynamometer type wattmeter, moving coil works as pressure. The permanent magnet moving coil instrument is the most accurate type of dc measurement. Electrodynamic or dynamometer instruments electrical. Mar 03, 2019 thus shunt resistance limits the current in the moving coil to only a small fraction of the current being measured. Dynamometer type wattmeter construction and working principle. Electro dynamometer type inductor loudspeaker scribd. This fixed coil is divided into two sections so that a uniform magnetic field may be achieved at the centre.
Dynamometer type wattmeter instruments have uniform scale. The moving system of the instrument is attached to the soft iron piece and thus moves the pointer over the scale. Permanent magnet moving coil pmmc the principle operation of pmmc is based upon the principle. The signals which vary in discrete steps and have only finite. Electrodynamometer electrodynamics type instruments.
When current flows in the solenoid, a pivoted softiron disc is attracted towards the solenoid and the movement causes a pointer to move across a scale. The deflection type dynamometer type wattmeter is a good example of an analog instrument. In a moving coil instrument, the damping torque is developed by a fluid friction damping. Since the coil is placed in the strong field of permanent magnets, a force is exerted on the current carrying conductors of the coil which produces deflecting torque. Electrodynamometer electrodynamics type instruments the necessity for the a. The fixed coil is split into two equal parts which are placed close together and parallel to each other. Jun 04, 2018 a electrostatics b moving iron c moving coil permanent magnet type d moving coil dynamometer type answera 3. Dynamometer type moving coil instruments in this instrument the permanent magnet is replaced by one or two fixed coils which carry current to be measured or a current proportional to the voltage to be measured and which are connected either in series or parallel with the moving coil. Moving coil instruments permanent magnet moving coil mechanism. Mcq on measuring instruments 4 how engineering works. Since the current of the moving coil is carried by the instrument springs, it is limited to values, which can be carried safely by springs. Moving iron instruments are generally used to measure alternating voltages and currents. It uses for measuring the power of both the ac and dc circuits.
Dynamometer type wattmeter electrical technology duration. The dynamometer type of voltmeter takes about five times as much current as the d c voltmeter of the same rating and consumes an appreciable amount of power. A permanent magnet moving coil pmmc meter also known as a darsonval meter or galvanometer is an instrument that allows you to measure the current through a coil by observing the coil s angular deflection in a uniform magnetic field a pmmc meter places a coil of wire i. Dynamometer type instrument,electrical engineering.
In a dynamometer type of moving coil instrument a swamping resistance is provided inorder to. The simple view of construction of moving coil instrument is shown in the figure. This means that the torque in electrodynamometer instruments must have a finite value and unidirectional for ac and dc quantity unlike pmmc instruments. Jul, 2016 reversing the current, reverses the field due to fixed coil as well as the current in the moving coil so that the direction of the deflection torque remains unchanged. Now let us look at constructional details of electrodynamometer. Feb 15, 2018 dynamometer type instrument,electrical engineering dynamometer type instrument. The coils are usually air cored to avoid hysteresis, eddy currents and other errors when the instrument is. Working principle and construction of pmmc polytechnic hub. Mar 16, 2018 pmmc stands for permanent magnet moving coil. Electrodynamic type instrument construction and working.
In order to read the ac quantities using a moving coil instruments, the. Dynamometer type wattmeter working your electrical guide. The basic working principle of a pmmc instrument is the same at that d arsonval galvanometer but it slightly differs from the d arsonval galvanometer in construction. Hi friends, in this article, i am going to discuss about moving coil instrument working principle and other related information. Dynamometer type instrument,electrical engineering dynamometer type instrument. The fixed coil is splitted into two equal parts, which are placed. Moving coil instruments permanent magnet moving coil. Dynamometer type instrument construction and working. A dynamometer type wattmeter primarily consists of two coils called fixed coil and moving coil. Mar 18, 2018 difference between the construction of pmmc and dynamometer instruments pmmc permanent moving magnet coil instrument 1 moving coil.
Advantages and disadvantages of moving coil instruments. Download as pptx, pdf, txt or read online from scribd. The following types of instruments are used for dual purpose. The coils are usually air cored to avoid hysteresis, eddy currents and other errors when the instrument is used on a. As the input value changes, the moving system or pointer exhibits a smooth continuous motion. Moving iron instruments attraction type and repulsion type. Moving coil instruments there are two types of moving coil instruments namely, permanent magnet moving coil type which can only be used for direct current and voltage measurements and the dynamometer type which can be used on either direct or alternating current and voltage measurements. View electrodynamometer ppts online, safely and virusfree. For measurement of higher currents by dynamometer type instruments, the instrument may be used by connecting the moving coil across a. Limited of current flows through the moving coil so as to avoid heating. This method cannot be used in instruments where the introduction of a permanent magnet required for producing eddy currents will distort the existing magnetic field as in moving iron or dynamometer type of instruments. Feb 11, 2019 dynamometer type moving coil instrument in hindi electrodynamometer type instruments working principle and construction in hindi dynamometer type moving coil instrument in hindi.
The instrument whose working depends on the reaction between the magnetic field of moving and fixed coils is known as the electrodynamometer wattmeter. In moving iron instruments the movable system consists of one or more pieces of speciallyshaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. Permanent magnet moving coil instrument pmmc working and. The moving is air cored and is mounted on a pivoted spindle and can move freely. Deflection torque is proportional to the square of the current. Dynamometer type instrument and its working principle. The pmmc stands for permanent magnet moving coil and it is also called as darsonval instruments. Dynamometer type wattmeter construction and working.
So in order to limit the current we have connect the high value resistor in series with the moving coil. A permanent magnet moving coil pmmc meter also known as a darsonval meter or galvanometer is an instrument that allows you to measure the current through a coil by observing the coil s angular deflection in a uniform magnetic field. The dynamometer instrument is used to measure alternating current or voltage, the moving coildue to its inertia takes up a position where the. Following type of instrument is used to measure very small currents of high frequency, options are. Measuring instruments the device used for comparing the.
For these reasons this method is used in hot wire, moving coil and induction type instruments. It is recommended to read before going to understand the torque equation. A permanent magnet type moving coil instrument is shown in fig. The instrument in which the coil rotates between the magnetic field of the permanent magnet for measuring the dc such type of instrument is known as the moving coil instrument. Jan 15, 2019 what is a permanent magnet moving coil pmmc. These instruments essentially consist of fine wire moving coil placed in the magnetic field produced by another fixed coil when carrying currents. Measurement and instruments objective questions and answers pdf free download. Types of ammeters, voltmeters electrical instruments. Types of mechanical measuring tools and gauges used on ships. Electrodynamometer type instruments construction and operation. Moving iron instruments can be used a to measure dc currents only b to measure ac currents only c to measure a.
A permanent magnet is used to produce magnetic flux and a coil that carries the current to be measured moves in this field. Electrodynamometer instruments or electrodynamic instruments have fixed coil divided into two sections and a moving coil. It is a permanent magnet moving coil instrument plus a rectifier is also suitable for acdc measurements. They are used on board to assist in regular maintenance of electrical equipment or when precise measurements are required. Measurements and instrumentation 2 mark questions answers pdf.
The use of moving coil as pressure coil is a natural consequence of design requirements. Moving coil instrument working principle your electrical guide. The other moving coil instrument is a dynamometer type which can measure ac and dc work. The controlling torque is provided by two springs which also serve the additional purpose of leading the current into and out of the moving coil. It is one of the two types of moving coil instruments used to measure dc work only. Dynamometer type instrument and its working principle about. There are two types of coils present in the electrodynamometer. Pmmc permanent moving magnet coil instrument 1 moving coil.
Thus shunt resistance limits the current in the moving coil to only a small fraction of the current being measured. The moving coil is wound with many turns of enamelled or silkcovered copper wire. Measurement is an act or the result of comparison between the quantity and a predefined standard. Hi friends, in this article, i am discussing the dynamometer type wattmeter working principle and related information, if you are interested in it then you at the right place these are basically moving coil instruments. This instrument can measure ac as well as dc quantities. Advantages are, moving coil instruments consume quite less power. If two coils are connected such that, current proportional to the load voltage, flows through one coil and current proportional to the load current, flows through another coil, the meter can be calibrated directly in watts. Attraction type moving iron instruments the principle is when an non magnetized soft iron piece is placed in the magnetic field of the coil. So in order to limit the current we have connected the high value resistor in series with the moving coil. For measurement of higher currents by dynamometer type instruments, the instrument may be used by connecting the moving coil across a shunt and fixed coils as shown in the figure below. In electrodynamometer type wattmeter, moving coil works as pressure coil. Pmmc instrument working principle permanent magnet.
Download practical maritime ebooks with amazing bonuses. Fixed coil is provided for the sake of production of magnetic field. Therefore, such instruments can be used for the measurement of a. The moving is air cored and is mounted on a pivoted spindle and can moves freely. Difference between the construction of pmmc and dynamometer instruments. Moving coil instrument working principle your electrical. Dynamometer type moving coil instruments in this instrument.
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