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