Theory of . Explanation:-. (c) Electronic measuring instruments. Found inside – Page 179If the instrument is under - damped the pointer oscillate about the final position and take some time to come to rest . ... Eddy current damping ( iii ) Fluid damping Classification of MI instrument MI instruments are of two types : 1. Required fields are marked *. Eddy current damping is the most efficient form of damping. If the instrument is under-damped, the pointer will oscillate about the final position for some time before coming to rest. In this method, a small weight is attached to the moving system, which provides necessary controlling torque. © https://yourelectricalguide.com/ deflecting torque, controlling torque, damping torque. Found inside – Page 53measuring. instruments. and. T. S. C. C. S. Tests and measurements are important in designing, evaluating, ... There are three main types of damping used – eddy-current damping, air-friction damping and fluidfriction damping. These types of instruments are used for high voltage AC measurements as well as . The pointer comes to rest at a position where controlling torque is equal to the deflecting torque.In this method, controlling torque (Tc) is proportional to the sin of angle of deflection (θ) i.e. 1. Types of Measuring Instruments: With the need to create quality products that meet design tolerances, a large number of firms use measuring instruments with high accuracy and precision. #1. Eddy current damping cannot be used in these instruments as introduction of a permanent magnet for the purpose would distort the working magnetic field of the instrument. Movable magnet type measuring instrument US6679122B2 (en) 1998-05-15: 2004-01-20: Dresser, Inc. Pressure gauge having a dampener mechanism with attachable housing WO2018060984A1 (en) * 2016-09-29: 2018-04-05: Vastech Holdings Ltd. Electric motor having a diametric coil The figure shows a typical type of damping system provided in the instrument, where damping is achieved by a moving piston in an air syringe. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website. Found inside – Page 147Figure 6.2 shows the deflection of instrument in different types of damping. Critically damped instruments are preferred. ... damping torque can be provided by the following methods. Electrical Measuring Instruments and Measurements 147. 1. D'Arsonval Galvanometer 10. Eddy current damping. A transfer instrument is one that may be calibrated with a d.c. source and then used without modification to measure a.c. Found inside – Page 68(a) Deflecting device (b) Controlling device (c) Damping device (d) All of the above 7. ... is measurement (a) moving iron type (b) permanent magnet type (c) electrodynamics type (d) hot wire type (a) Indicating or deflecting type ... Snoek relaxation, proposed in 1941 (), is suited for equipping materials with damping properties and maintains those over long-term exposure to vibrations.Several bcc (body-centered cubic) systems show Snoek-type damping behavior, where the mechanical energy loss originates from the stress-induced ordering of interstitials (12, 13).However, these Snoek-type high-damping alloys generally showed . Fluid Friction Damping 9. X 1.7.2.6 Chemical seals / Protective buffers 110 1.7.2.7 Protective devices 110 1.7.2.8 Measuring arrangements 111 1.7.2.9 Installation and start-up 112 A concept called damping is of critical importance in a transmitter's performance. Found inside – Page 384Different types of accelerometer also vary in terms of the type of spring element and form of damping used. Resistive potentiometers are one such displacement-measuring instrument used in accelerometers. These are used mainly for ... The controlling torque in indicating instruments may be provided by one of the following two methods: This is the most common method of providing controlling torque, in electrical instruments. T = K 1 . Measuring instrument. A damping torque is produced by a damping or stopping force which acts on the moving system only when it is moving and always opposes its motion. Categories Instrumentation, Basic Electrical, Measurement. Found inside – Page 11310.1 Introduction 10.2 Analogue instruments Figure 10.1 10.3 Moving-iron instrument Tests and measurements are ... There are three main types of damping used—eddy-current damping, air-friction damping and fluid-friction damping. 1.6 Rectangular type 1.7 Permanent Magnet Moving Coil (PMMC) instrument One of the most accurate type of instrument used for D.C. measurements is PMMC instrument. Weighing scale - used to measure weight. Aluminum former is Based on the rule of "Fleming left hand", if the thumbnail of the left hand, middle and forefinger are at 90 degrees with each other. Fig. When the current to be measured is passed through the coil, then coil produces a magnetic field and attracts the oval-shaped disc, hence disc will swing into the coil. Measuring Instruments. This damping torque acts only when the pointer is in motion and always opposes the motion. Most transmitters incorporate a sensor that measures the input variable and delivers an output common to 4–20 m A. They are made as ammeters and voltmeters and can measure both ac and dc currents and voltages respectively. Found inside – Page 48Depending on the degree of damping, three types of motion of the deflection system can be distinguished (Fig. ... For measuring instruments with the degree of attenuation s 1 (aperiodical), the deflection system would take infinitely ... Unless a child keeps pumping a swing, its motion dies down because of damping. (1). Air friction damping b. . Found inside – Page 70These types of damping are illustrated in fig. D1. In many measuring instruments, critical damping is often intentionally introduced in order to facilitate the observation of readings. Daniell cell. A primary CELL in which the positive ... Found inside – Page 312Instead , spring control is used in almost all types of indicating instruments . 10.6 DAMPING DEVICE The major function of the damping device is to produce a damping force while the moving system is in motion . The damping force should ... etc Motion Damping torque is . In reaction to modifications in the input variable, a process transmitter typically “measures” a process variables such as, flow, intensity, temperature, pressure-and generates an output. The decrease in temperature is 0.02 x°C where x is the altitude in meter. A few test measurements determine the bandwidth, blocksize, trigger settings, windowing or not, etc. The measuring instruments may be classified as follows: Absolute instrument & Secondary instruments: Absolute instrument measures the process variable directly from the process without the use of conversion. The chamber is completed by providing a cover plate at the top. An analog instrument is one in which the output or display is a continuous function of time and bears a constant relation to its input. A more sophisticated method for damping pulsations seen by a pressure instrument is called a snubber, Used for dampening and filtering, the snubber has a metal disc available in four grades of porosity Due to the large filter area, the snubber has less tendency to clog than orifice-type devices. Its scale is linear. C. Both A.C and D.C. 32. Fig. Fig. Basically, there are three types of Force or torque act upon the Measuring Instrument. The essential components in this type of damping are a permanent magnet; and a light conducting disc usually of alumninum. Found inside – Page 1493 Measuring Instruments 1. Introduction and classification . 2. Electrical principles of operation . 3. Electrical indicating instruments — Essential features - Deflecting devices - Controlling devices — Damping devices . 4. Controlling System 4. To be effective the, When the piston moves into the chamber, the air inside is compressed and the pressure of air thus built up, opposes the motion of the piston and hence the whole of the, The arrangement of the above figure(b), consists of an aluminium vane which moves in a quadrant (sector) shaped air chamber. if(typeof __ez_fad_position != 'undefined'){__ez_fad_position('div-gpt-ad-yourelectricalguide_com-large-mobile-banner-1-0')}; One of the most accurate instruments used for both AC and DC measurement is moving iron instrument. Thermal effect ———————————Hot-wire instruments. Maxwell bridge configuration for measurement of inductance and De Santy's bridge for measurement of capacitance Maxwell Wein bridge configuration for measurement of inductance and De Santy's bridge for measurement of capacitance A moving iron instrument can be used for. This torque is proportional to the strength of the magnetic field and the current produced. - Clinometers measured both inclines ( Positive slopes) and declines (Negative slopes) using three . Here we are interested in electrical measuring instruments so we will discuss about them in detail.Electrical instruments measure the various electrical quantities like electrical power factor, power, voltage and current etc. The damping torque should be of such a magnitude that the pointer quickly comes to its final steady position, without overshooting. A concept called damping is of critical importance in a transmitter’s performance. (b) is preferred. Non-Precision Equipment: Steel Rule:- Its sensitivity is lesser than M.I. Analog Measuring Tools. Found inside – Page 168Tests and measurements are important in designing, evaluating, maintaining and servicing electrical circuits and ... There are three main types of damping used – eddy-current damping, air-friction damping and fluid-friction damping. All Right Reserved. - Clinometer is an instrument for measuring angles of slop, elevation or depressio of an object with respect to gravity. Found inside – Page 6-3The below given options matched the type of damping mechanism used in instruments. Choose the incorrect one. (a) Air friction damping → Moving iron (b) Fluid friction damping → Electrostatic instrument (c) Eddy current damping → EMMC ... The figure shows a typical type of damping system provided in the instrument, where damping is achieved by a moving piston in an air syringe. Moving Iron Instrument Multiple Choice Questions and Answers. 21. 1. Whenever a current caring conductor is located within a magnetic field, then it experiences a force that is perpendicular to the current & the field. A moving iron type ammeter has far turns of thick wire so that. Deflecting Torque. On the other hand, if the instrument is over damped, the pointer will become slow and lethargic. 1.7.2.4 Damping the measuring system 110 1.7.2.5 Temperature considerations 110. Electromagnetic induction effect ———Induction type instruments. And if both the fluxes are produced by the same alternating current, then. Found inside – Page 27This is the most efficient type of damping and is largely used in permanent magnet moving coil instruments , hot wire instruments and induction type instruments . 3.4 TYPES OF ELECTRICAL INSTRUMENTS Electrical measuring instruments may ... All Rights Reserved by Electrical Engineering Info. B. errors such as induced emfs, frequency variations, and harmonic-current components are only present in ac instruments. The voltmeter shown has a range 0- 100 V, i.e. Basically there are three types of measuring instruments and they are (a) Electrical measuring instruments (b) Mechanical measuring instruments. Suspension type of measuring instruments can only be used in a vertical position.The taut suspension has a flat ribbon suspension both above and below the moving element, with suspension kept under tension by a spring arrangement.The advantage of this suspension is that exact levelling is not required if the moving element is properly balanced. if(typeof __ez_fad_position != 'undefined'){__ez_fad_position('div-gpt-ad-yourelectricalguide_com-box-3-0')};In order to ensure proper operation of indicating instruments, the following three torques are required: One important requirement in indicating instruments is the arrangement for producing operating or deflecting torque (Td) when the instrument is connected in the circuit to measure the given electrical quantity. The damping force can be varied by varying the projection of the magnet over the circular disc. Vernier Callipers - it is an instrument that is used in measuring short straight lines. Intrinsic Constants of Galvanometer 12. There are three types of damping instruments: 1.Critical damp- Pointer rises quickly to its final position without oscillation. The aluminium piston should be carefully fitted so that it does not touch the wall otherwise a serious, Electrical and Electronics Measurements by S. Chand, This form of damping is similar to air friction damping. Where, ϕ 1 m, ϕ 2 m = maximum fluxes produced by the currents. <a title="PMMC Instrument MCQ . (c) Eddy Current Damping: In electrical measuring instruments, the use of eddy currents has been made as an electromagnetic breaker or damper. 189. Magnetic effect ——————————- Moving-iron instruments. Found inside – Page 49The dynamic characteristics of measuring instruments reflect the relation between the change in the output signal and an ... coefficient in the static state, !0 is the angular frequency of free oscillations, and ˇ is the damping ratio. Damping torque in measuring instruments provided by fluid friction damping is mainly used. Advertisement. Found inside – Page 130Daempfung von Messgeraeten ( Damping of measuring instruments ) , W. HOFMANN . ... frequent checking of test instruments with reliable working standards is essential ; if possible , correct type of instrument should be used in every ... Damping force in any electrical instrument is necessary because it brings the pointer at rest quickly. The output of the transmitter must be updated and changed accordingly as the input variable modifications. In this method, discs or vanes attached to the spindle of the moving system are kept immersed in a pot containing oil of high viscosity. The eddy current damping is the most efficient and is based on the principle that whenever as sheet of conducting but non-magnetic material like copper or aluminum moves in a magnetic field so as to cut . The movement of a coil in a magnetic field produces a current in the coil which interacts with the magnetic field to produce a torque. 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. three main types of damping used — eddy-current damping, air-friction damping and fluid-friction damping. These eddy currents react with the field of the magnet to produce a force which opposes the motion according to Lenz’s Law. The controlling torque (Tc) opposes the deflecting torque and increases with the deflection of the moving system. Two types of moving iron instruments are manufactured. PMMC ammeter have uniform scale because of eddy current damping they are spring controlled their deflecting torque varies directly as current both spring controlled and having deflecting torque varies directly as current 2. Since the torsion torque of a spiral spring is proportional to the angle of twist, the controlling torque (Tc ) is directly proportional to the angle of deflection of pointer (θ) i.e. i want alebelled diagram of damping, controlling torque, Your email address will not be published. The weight of the instrument is heavier than that of air friction damping instrument. . Found inside – Page 314Deflecting torque is produced by (a) magnetic effect (b) damping effect (c) thermal effect (d) electrostatic effect 5. Which type or degree of damping is preferred in most of the measuring instruments (a) under damping (b) over damping ... Thus the spring controlled instruments having uniform scale. This article lists 100+ Measurement and Instrumentation MCQs for engineering students.All the Measurement and Instrumentation Questions & Answers given below includes solution and link wherever possible to the relevant topic.. The moving iron type instruments are one of the types of measuring instruments used for measuring voltage or current. The damping ratio is a measure of describing how oscillations in a system die down after a disturbance i.e. Chemical effect ——————————–Electrolytic instruments. 1. The electrical measuring instrument of claim 6 wherein said portion of said damping member is a fingerlike part projecting from said damping member. (b) mass of the pointer. Theory of Attraction Type Moving Iron Instrument Suppose when there is no current through the coil, the pointer is at zero, the angle made by the axis of the iron disc with the line perpendicular to the . This is the most effective and modern process of damping in measuring instrument. 1.6 Rectangular type 1.7 Permanent Magnet Moving Coil (PMMC) instrument One of the most accurate type of instrument used for D.C. measurements is PMMC instrument. Eddy current . Found inside – Page 341In an attraction type moving Iron instrument , the of 4.5 22 gives a full scale deflection of 30 mA . damping torque is ... Damping torque in measuring instruments provide ( a ) Moving iron ( b ) Moving coil by Fluid friction damping is ... In the arrangement shown in fig (a), a light aluminum piston is attached to the spindle that carries the pointer and moves with a very little clearance in a rectangular or circular air chamber closed at one end. The output of the transmitter must be updated and changed accordingly as the input variable modifications.. Damping is the amount of time required to reach 63.2 percent of the transmitter's final value after a step change has been applied to the input, in addition to the update time. Introduction to measuring instruments and Classification of Measuring Instruments 2. As the pointer moves, the vanes swing and compress the air. Moving iron attraction type instrument b.
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