To study the advantage and limitation of pmmc instruments. Learning how to use those meters and using them to measure the current, voltage, and resistance of an electric circuit. Second, a method is needed to indicate the amount of coil movement. The coil resistance increases with increase in the temperature. What is permanent magnet moving coil or pmmc instrument. With this setup, we can apply the currentdivider formula. In a pmmc instrument, if the control springs are eliminated the instrument can be used for measuring the quantity of electricity passed through the coil. Pmmc instruments, galvanometer, dc voltmeter, dc ammeter 1. Here we have listed different units wise downloadable links of electrical measurements notes where you can click to download respectively. Understanding the structure of the ammeter, voltmeter. First, a way must be found to return the coil to its original position when there is no current through the coil. Worryometer a b c d e f what can you do to either reduce the chance of this happening or reduce the impact if it does occur.
Dc ammeter are mainly pmmc instruments, mi can measure both ac and dc currents, also electrodynamometer type thermal instrument can measure dc and ac, induction meters are not generally used for ammeter construction due to their higher cost, inaccuracy in measurement description of different types of ammeters pmmc ammeter. A permanent magnet moving coil pmmc is one such instrument which is popularly. The basic construction of pmmc is shown in above fig. According to the fundamental law of electromagnetic force, the coil will rotate in the magnetic field when it. Pmmc instrument pmmc instrument, galvanometer, dc ammeter, dc voltmeter, series ohm meter. The presentation covers, pmmc instrument construction and working. Pmmc instruments, galvanometer, dc voltmeter, dc ammeter. This permanentmagnet movingcoil meter movement is the basic movement in most measuring instruments. The action of the permanent magnet moving coil pmmc instrument is based on the motoring principle when a currentcarrying coil is placed in the magnetic field produced by the permanent magnet, the coil experiences a force and moves. We can see that the current i divides into the branches of the pmmc and the shunt resistor. The construction and working of a pmmc instrument article716. Permanent magnet moving coil or pmmc instrument definition. Emitter follower at the condition of vin 0, vp should be set to give zero meter reading, vm 0. Pmmc measurement free download as powerpoint presentation.
Pdf eec 126 instrumentation theory farouq osuolale. Thus, oscillations of the meter pmmc instrument are damped out. Therefore, the potentiometer r5 is for the zero adjust. Pmmc instrument working principle permanent magnet moving coil instrument the permanent magnet moving coil pmmc instrument is an electromechanical meter that can be connected with additional components to function as an ammeter, a voltmeter, or an ohmmeter. The working principal of this instrument is same as that of the darsonval type of galvanometers,the difference being that a direct reading instrument is provide with a pointer and a scale. It is commonly called the darsonval movement because it was first employed by the frenchman. Permanent magnet moving coil mechanism pmmc mathematical. The first problem is solved by the use of hairsprings attached to each end of the coil as shown in fig. From the given problem, we can create the equivalent circuit as shown on figure 1. The meter is found to make 80 revolutions in 8 sec. 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 coils angular deflection in a uniform magnetic field. They are a centre zero pmmc meter a true rms meter and a moving iron instrument from ee 419 at indian institute of technology, chennai.
Measurements and instrumentation questions and answers. If transistors q1 and q 2 are identical, vbe1 vbe2 vv v v v vv v vme e in be p be in p. Pmmc instrument working principle permanent magnet. Permanent magnet moving coil or pmmc instruments are the most accurate type for the measurement of dc current or voltage. When a current carrying coil is placed in the magnetic field produced by permanent magnet, the coil experiences a. Measurement dee1012 pages 1 50 text version fliphtml5. The magnetic field strength and spring tension decrease with increase in temperature. How a pmmc meter can be used as voltmeter and ammeter. They are very sensitive and maintain a high degree of accuracy over long periods. To avoid effect on circuit current, ammeter resistance should be low.
Permanent magnet moving coil instrument or pmmc instrument the current i is shown which breaks into two components at the point the two components are is and before i. Ohms law and kirchhoffs rules is the coil and the scale of pmmc meter could be calibrates to fundamental for understanding of dc circuit. Various error in pmmc instrument electrical concepts. Permanent magnet moving coil instrument pmmc working and.
Write any two advantages and disadvantages of digital voltmeter. It is one of the simple and most used instrument on board with sophisticated names. When a current carrying coil is placed in the magnetic field produced by permanent magnet, the coil experiences a force and moves. Electrodynamometer type, induction type, single phase and three phase wattmeter. Measurements and instruments viva short questions and. Explain the purpose of schmitt trigger in digital frequency meter. The working principle of the ballistic galvanometer is very simple. Understanding the structure of the ammeter, voltmeter, and ohmmeter. Pmmc with ac measurement rectifier alternating current. As long as the instrument is connected in the circuit and measurable.
The moving coil is either rectangular or circular in shape. The instruments which use the permanent magnet for creating the stationary magnetic field between which the coil moves is known as the permanent magnet moving coil or pmmc instrument. Ammeter, voltmeter, wattmeter, frequency meter, power factor meter etc. Measurement introduces students to the basic concept of electrical instrument and measurement. Pmmc instruments construction and working principle. They are a centre zero pmmc meter a true rms meter and a. Pmmc instruments pdf in pmmc meter or darsonval meter or galvanometer all are the same. The electrical measurements notes pdf em notes pdf book starts with the topics covering control and damping torques, design considerations type of p. The basic pmmc instrument is sensitive to the temperature. Permanent magnet moving coil mechanism pmmc in pmmc meter or darsonval meter or galvanometer all are the same instrument, a coil of fine wire is suspended in a magnetic field produced by permanent magnet. Download the same notes in small file size from 2nd link. Working principle and construction of pmmc polytechnic hub.
The weakening of spring can be reduced by careful use of material and preaging during manufacturing process. Ebooks, materials, notes, previous solved papers, questions and answers with explanations, faq, mcq. Applications of pmmc permanent magnet moving coil instruments are acknowledged to be the best type of all d. It operates on the principle that the torque is exerted on the moving coil placed in the field of the permanent magnet.
In the measurement of direct currents and voltage ii. The action of these instruments is based on the motoring principle. Pmmc, mi, emmc or edm, esv instruments measurement. Ammeter working principle and types of ammeter electrical4u.
The pmmc stands for permanent magnet moving coil and it is also called as darsonval instruments. Electrostatic voltmeters electrometer type and attracted disc type extension of range of e. Measurements and instrumentation questions and answers pdf free download for ece mcqs objective type interview questions lab viva manual gate cat syllabus. Select the yellow config button select firmware upgrade 4 then hit ok select what you would like to upgrade. The galvanometer which is used for estimating the quantity of charge flow through it is called the ballistic galvanometer. The pmmc consumes less power and has great accuracy. The moving system of the instrument carries an inked pen pointer which rest lightly. Electrical and electronic measurements kuestion free.
Download as ppt, pdf, txt or read online from scribd. Measurements and instrumentation question bank ee8403 pdf free download. Download practical maritime ebooks with amazing bonuses. Pmmc instruments pdf pmmc instruments pdf pmmc instruments pdf download. It covers the basic principles of measurement, safety precautions and meter calibration. The meter movement as it appears when fully assembled is shown in figure 6. Pmmc temperature compensation instrumentation tools. Meters, double element and three element dynamometer wattmeter, errors and compensations, measurement.
Application and database press ok, then follow the prompts and allow the meter to reboot. Stationary magnet in the present days we are using u shaped permanent magnet in pmmc instrument in this magnets high field intensities,high coericive force. Pmmc type moving iron type dynamometer type hot wire type, electrostatic type, induction type. The working principle of pmmc instruments are same as that of darsonaval type of galvanometer, difference being that a direct reading instrument is provided with pointer and scale. Students will also use measurement devices such as analogue meters, dc and ac meters, analogue and digital multimeters, oscilloscopes, signal generators and power meters during practical session. The permanent magnet moving coil instruments are most accurate type for direct current measurements. Here you can download the free lecture notes of electrical measurements pdf notes em pdf notes materials with multiple file links. It has efficient damping characteristics and is not affected by stray magnetic field. From the above two equations we can write, where, m is the magnifying pmmc instrument of the shunt. Electrical measurements pdf notes em pdf notes smartzworld. Measurement and instruments objective questions and answers pdf free download. It has uniformly divided scale and can cover arc of 270 degree.
The material which we are using to made magnet like alcomax and elnico which provide high field strength. They are used on board to assist in regular maintenance of electrical equipment or when precise measurements are required. Ee8403 question bank measurements and instrumentation. The series resistance should be much larger than the impedance of the circuit being. Permanent magnet moving coil instruments pmmc the permanent magnet moving coil instruments are most accurate type for direct current measurements. Pmmc with ac measurement free download as powerpoint presentation. It can be modified as ammeter or voltmeter with suitable resistance. Since the coil winding in pmmc meter is small and light, they can carry only small. Pmmcthe permanent magnet moving coil instrument is the most accurate type for d. Measuring instruments classification deflecting, control and damping torques ammeters and voltmeters pmmc, moving iron type instruments expression for the deflecting torque and control torque errors and compensations, extension of range using shunts and series resistance.
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