It is also mathematically the easiest form of damping to apply to . As the pointer moves, the disc cuts across the magnetic field and eddy currents are induced in the disc. In a megger when not in operation, the needle shows a resistance of. Electrical Measuring Instruments - Engineering Notes Online PDF Vibration Measurement Techniques: Basics Introduction . (PDF) VIBRATION MEASURING INSTRUMENTS | Rocker Thacker ... Electrical Measurement - Apps on Google Play PDF Chapter 4 Measurement of Surface Wind MEASURING INSTRUMENTS "The device used for comparing the unknown quantity with the unit of measurement or standard quantity is called a Measuring Instrument." OR "An instrument may be defined as a machine or system which is designed to maintain functional relationship between prescribed properties of physical variables & could include for damping torque eddy current damping is used. Measuring the Q-factor of a resonator with the ring-down ... Measuring Instruments: Classification, Absolute and secondary instruments, indicating instruments, control, balancing and damping, constructional details, characteristics, errors in measurement, Ammeters, . DYNAMIC RESPONSE OF INSTRUMENT SYSTEMS - ScienceDirect Moving Iron Instruments Attraction type M. I. (d) photo conductive cell. Measuring Instruments 9 Disadvantage of fluid damping 1. [Solved] Which of the following methods are NOT used to ... Methods of measurement (direct measurement , Indirect measurement) Measurement of quantity is essentially an act or the result of comparison between the amount of quantity is unknown and the standard quantity is known. Measuring Instruments 9 Disadvantage of fluid damping 1. Oil creeps out if the sealing is not perfect. D'Arsonval Galvanometer 10. The Oberst method is widely used for the measurement of the mechanical properties of viscoelastic or damping materials. PDF Electrical Measurement & Measuring Instruments Damping torque acts only when the pointer is in motion and always opposes the . Damping Torque in Indicating Measuring Instruments: We know deflecting torque, controlling torque and damping torque are present in measuring instruments.When a deflecting force is applied to the moving system, it deflects and it should come to rest at a position where the deflecting force is balanced by the controlling force. Electrical Measuring Instruments Principle of Operation depends for their action on one of the many physical effects of an electric current or potential and are generally classified according to which of these effects is utilized in their operation (Electrical Measuring Instruments Principle of Operation). this torque is also used to minimize the accelerating or vibration effect of pointer.there are three methods to produce damping torque in the measuring instrument. Instruments 3. Measuring Instruments Classification 1. The measurement is the act or the result of a comparison between an unknown quantity and a known quantity. of the pointer and to bring it quickly to its final deflected position ,a damping torque is provided in the indicating instruments. It highlights the choice of instrument dynamic response for a particular measurement. ⇒ The disc of an instrument using eddy current damping should be of . Fluid Friction Damping 9. Damping torque or damping forces is the speed deviation of an electromechanical torque deviations of a machine while the angle deviation is called synchronizing torque [1]. It is one of the two types of moving coil instruments used to measure dc work only. 31. 4.2.1 Wind Estimation In order for damping to be a useful tool for the technician in mitigating measurement noise, it must be adjustable. A cadmium sulphide cell is a. It is not suitable for portable instruments. The actual method of producing the deflecting torque depends upon the type of instrument. Before going into the details you must understand the need for a damping system in a measuring instrument. 2. Unit 2. 11. DMA (or dynamic mechanical thermal analysis (DMTA)), measures the stiffness and damping properties of materials as a function of time, temperature, and frequency by applying a sinusoidal load to a specimen and measuring the resultant deformation, whilst the sample is subjected to a controlled . Definitions of accuracy, precision, error, resolution and sensitivity - important electrical quantities to be measured - their units -names of instruments to measure them - classification of instruments -different types of torques (deflection, controlling and damping torques) in the indicating . When a measuring instrument malfunctions, or when no such instrument is available, the wind direction and speed may be estimated subjectively. laboratory type electrostatic instruments. Damping torque or restoring torque i. Answer (1 of 8): Without damping the indicator will oscillate about the measured value, only settling slowly to the final state. This piston is placed in a chamber which is closed at one end. This contribution shall review the most important damping phenomena that are related to musical instruments and review measurement methods that are employed to quantify damping values. 2. Critical damping just prevents vibration or just allows the object to return to rest in the shortest time. Damping treatment is a standard practice in many industries for controlling excessive vibration at resonance. The motion of the disc is always opposed by a frictional drag on the disc. 1.7.2.3 Mounting the measuring instrument in position 110 1.7.2.4 Damping the measuring system 110 Deflecting System 3. Damping curves: 12. Damping System 7. • It is the most efficient and is based on the principle that whenever a sheet of conducting 10 μA - 100 mA. Active Feedback Control and Shunt Damping. W. Broughton, in Adhesives in Marine Engineering, 2012 6.3.1 Dynamic mechanical analysis (DMA). Ordinary ammeters, voltmeters, and watt-meters fall into this category ().Integrating instruments: The instruments that add up the electrical quantity, that is, electrical energy and measure the . Air Friction Damping 8. A measuring instrument is a device in which . 1.6.3 Eddy Current Damping This method is mainly based on Faraday's law and Lenz's law. Damping, restraining of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipation of energy. Megger is an instrument used for the measurement of: a) High resistance and insulation resistance b) Medium resistance c) Low resistance d) Leakage current. Ans: Eddy current damping, Q: How eddy current damping is used? Eddy current damping 2. 1. The chamber has a small opening. In a measuring instrument, the damping torque is necessary to bring the moving system to rest to indicate steady reflection in a reasonable short time. The method is to compute the damping ratio η of the foodstuff to be measured by an equation η=Δf/f 0, in which f 0 is the intrinsic resonance frequency of the foodstuff, which is obtained by measuring the rectangular slice of the foodstuff, on which a vibration is applied, and Δf is a half-power bandwidth. Read: Comprehensive viva questions of eee: Electrical Measuring Instruments part-3 Spring Control method ii Gravity control method 3. Fig. The fluid friction damping can be used for laboratory type electrostatic instruments. Wax is one of them, and it's mostly used in musical instruments. Comparison of Controlling Systems 6. Different modes of vibrations of plates and of string instruments can be studied with optical methods. Vijay Balu Raskar - Electrical Maintenance - Polyphase Circuit Junior Science College ( Std - XI ) - Syllabus Theory - "Measuring Instruments" Why ? Vibration reeds are employed in: a) Frequency meter b) Power factor meter . Electrical energy is being used in the manufacturer of many commodities. Air friction- It consists of a light aluminium piston attached to the moving system of instrument. 41. Instruments Repulsion type M. I. 1. Fluid Friction Damping 9. These are : (i) Deflecting force (ii) controlling force (iii) damping force Controlling System 4. Vibration The aim of the present study is to measure damping . This chapter discusses the dynamic response of instrument systems. Air friction damping ii. The instrument has to be used only in vertical position. The permanent magnet moving coil instrument is the most accurate type of DC measurement. Air Friction Damping System . (d) Electromagnetic Damping 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. E. Electrostatic instrument This instrument works on the principal of electrostatic . Measuring instrument. 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.. A distinction is also made between analog measurement and digital measurement. This type of damping is often considered for this type of second order system because it is reasonably representative of the energy dissipation methods in many engineering structures. And the damping ratio η thus . Intrinsic Constants of Galvanometer 12. system loss factors (measure of energy Threaded or pressed into an instrument socket, the throttle screw orifice selected is based on the viscosity of the pressure fluid, rapidity of pressure fluctuations, and the amount of dampening effect desired. The other moving coil instrument is a dynamometer type which can measure AC and DC work. at 01:15. methods: (1) absorption (2) use of . Deflecting torque 2. •In the switched shunts method, the multi shunt resistors (R S1, R S2,…, R Sn) are connected in parallel with each other and a switch selects one of them for a selected range. Eddy Current Damping • In electrical measuring instruments, the use of eddy currents has been made as an electro-magnetic braker or damper (refer figure 2.6). There are different methods are used for measurement of low, medium and high resistance. . A distinction is also made between analog measurement and digital measurement. 2.Under damp- oscillations of the system will not be completely preventated. When a conductor moves The movement of the shaft is retarded because of the resistance which the air offers to the vane. Linear Averaging with a number of 4 is set, using an input channel trigger with a pre-trigger was set to capture . Unit 1 - Basics of Measuring Instruments. •When the range is changed two shunt resistors are connected in parallel (the switch makes the next Measuring instruments electrical maintenace 1. Spring Control 5. 1. but any suitable type of transducer may be used The damping shown in Figure 4 may consist only of the hysteresis of the . Ans: Because the aluminum disc rotates between the magnetic poles of a permanent magnet, induction eddy current and resulting from the damping. Deflecting System 3. Controlling System 4. The deflecting torque is produced by making use of one of the magnetic , heating, chemical electrostatic and electromagnetic induction effects of current or voltage and causes the moving system of the instrument to move from its zero position when the instrument is connected in an electrical circuit to measure the electrical quantity. Measuring Instruments - Electrical Engineering (MCQ) questions and answers. Measuring Instruments MCQ Question Answer. With any periodic disturbance in the measurement the indicator will never settle. ⇒ Which of the following is the best method for the measurement of . Damping Torque The force or torque which brings the pointer suddenly at its original position is called damping torque. 42. As shown in figure 8-125, a vane is attached to the shaft of the moving element and enclosed in an air chamber. •A special switch S (called make-before-break) must be used to protect the PMMC instrument. Different damping materials are available for various engineering applications. There are three types of damping instruments: 1.Critical damp- Pointer rises quickly to its final position without oscillation. Intrinsic Constants of Galvanometer 12. In a measuring instrument, the deflecting torque provides some deflection and controlling torque acts in the opposite direction to that of deflecting torque. This torque opposes the movement of the coil and slows the response. Moving Iron Instruments Attraction type M. I. In the analog method, measurement is done continuously, and the size of the signal is analogous to the measured value. DAMPING dx Fc dt = where c is the viscous damping constant with units of force per unit speed. The measured value is indicated on a pointer instrument that has got a scale (e.g. For connecting an instrument for measuring the amplitude, the same methods explained before also work fine. 3.Damping Torque 1.Deflecting Torque in Measuring Instruments The deflecting or operating torque (Td) is produced by utilizing one or other effects mentioned in the starting paragraph. In such instruments, a pointer moves over the calibrated scale to indicate the magnitude of electrical quantity being measured. It is difficult to keep the instrument clean due to leakage of oil. a. The relations between the various specific values that characterize damping are summarised, and their scopes are discussed. Damping System 7. Permanent Magnet Moving Coil or PMMC Instruments are the most accurate type for the measurement of DC current or voltage. damping and (4) vibration isolation. Spring Control method ii Gravity control method 3. Free and Forced Vibrations of Two Degree of Systems. The working principle of PMMC instruments are same as that of d'Arsonaval type of Galvanometer, difference being that a direct reading instrument is provided with pointer and scale. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Controlling torque i. Air friction damping The arrangement consists of a light aluminum piston which is attached to the moving system as shown in the figure below. The Stroboscope Method. . Basic Range. This section mainly describes the principles of measurement using vanes and rotating anemometers (cup and propeller types) and the response characteristics of these instruments. When a conductor moves The deflecting torque is used for deflection, the controlling torque acts opposite to the deflecting torque. (b) Fluid Friction Damping: In this method of damping light vanes or disc are attached to a spindle of the moving system and move in a damping oil. Air friction damping ii. a. 1.6.3 Eddy Current Damping This method is mainly based on Faraday's law and Lenz's law. ANSWER : A. The described damping device is particularly suitable for weighing machines and measuring instrun'ients in which a pointer cooperating with a suitably divided scale indicates the result of the. Meters, Double element and three element dynamometer wattmeter, errors and compensations, Measurement of unknown resistance, Method of measuring low, Measurement of inductance, Ballistic . The output of electric signal of the instrument will be proportional to the quantity which is to be measured. 3. Torque Equation 11. A Crystal Instruments Dynamic Signal Analyzer with EDM Modal software is used to acquire the measurement data and modal analysis. D'Arsonval Galvanometer 10. In the case of the RC filter circuit, the degree of damping (cutoff frequency) may be adjusted by changing the value or either R or C, with R being the easier component to adjust. Measurement is the process by which anybody can convert physical standards into a meaningful number. For example, damping in use, which take advantage of the resistance, the material particles of the force in. Essential Requirement of Indicating Instruments 1. Prof, DSCE, BLore-78 3 VIBRATION MEASURING INSTRUMENTS (Contd..) Two types of seismic transducers known as vibrometer and accelerometer are widely used. Analog and digital measuring methods. In the analog method, measurement is done continuously, and the size of the signal is analogous to the measured value. [5] (b) Explain the operation of a Wagner's earthing device. The instrument has to be used only in vertical position. A few test measurements determine the bandwidth, blocksize, trigger settings, windowing or not, etc. The value of deflecting torque must depend on the electrical signal voltage, resistance). Torque Equation 11. Electrical energy is being used in the manufacturer of many commodities. Electronic measuring instruments have advantages over instruments such as the moving-iron or moving-coil meters, in that they have a much higher input resistance (some as high as 1000 Mˇ) and can handle a much wider range of frequency (from d.c. up to MHz). A string musical instrument is a complex structure enclosing an air cavity, which is part of the system. (d) variation in flux density. 4/5/2014 Hareesha N G, Asst. 33. Comparison of Controlling Systems 6. 1. Question is ⇒ ____ damping method is common in moving coil instruments., Options are ⇒ (A) Eddy current, (B) Fluid, (C) Spring, (D) Air, (E) , Leave your comments or Download question paper. A system may be so damped that it cannot vibrate. METHODS OF PRODUCING DAMPING FORCE/TORQUE Damping torque in an instrument can be produced by using 1. The most popular method for the study of plates' vibrations is with Chladni patterns. 1. The eddy current damping is the most efficient and is . . The Electrical Measurements Notes Pdf - EM Notes Pdf book starts with the topics covering control and damping torques, design considerations Type of P.F. Multiple choice Questions and Answers on Measurement and Instrumentation 40.Loss of charge method is used to measure: a) Low R b) High R c) Low L d) High L. ANSWER : B. There are two types of wax are available namely beeswax (natural wax) and cosmetic wax. Introduction to measuring instruments and Classification of Measuring Instruments 2. TOPIC 2: DC METER 2.1.6 Compare Common Damping System In Indicating Instrument The following methods are used to produce torque. Various methods of connecting the oscilloscope to the tank circuit: (a) direct high-impedance probe connection, (b) loose inductive coupling, (c) autotransformer coupling and (d) weak capacitive coupling. availability of useful measurement methods and test facilities. 2. A photo electric transducers are used for the measurement of any phenomenon which can be used to produce. Various damping measures are used to prevent the display value of the mobile organ. The instruments with this type of damping must be kept always in a vertical position. Damping torque Analogue instruments are of second order type which has a damping factor δ 0.6 to 0.8 The type of damping is underdamped. Devices — located along the signal flow — which make up a measuring device and whose measuring characteristics (errors, chain of influences) are specific to the measuring device in question (Figure M 20).. 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