Electrical Measurement and Instrumentation, Study notes of Electrical Engineering

Download Electrical Measurement and Instrumentation and more Study notes Electrical Engineering in PDF only on Docsity! Electrical Measurement and Instrumentation By :- Sh Gulvender TOPICS LCR METERS Power Measurements in 3 phase circuit by (a) Two wattmeter method (b) Three wattmeter method Transducer Measurements of Temperature Transducer This article is about an engineering device. For the similarly named concept in computer science, see Finite state transducer. A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction. various types of transducer Types of Transducers in Practical Applications Onc Another Form of Form of mecccae —— P| Transducer ecw Transducer Ultrasonic Temperature Piezoelectric Pressure Transducer Transducer Transducer Transducer force measurement In physics, a force is any interaction that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F. The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object. Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the internal mechanical stress. Such internal mechanical stresses cause no acceleration of that body as the forces balance one another. Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of solid materials, or flow in fluids. torque measurement Torque, moment, or moment of force is rotational force. Just as a linear force is a push or a pull, a torque can be thought of as a twist to an object. In three dimensions, the torque is a pseudovector; for point particles, it is given by the cross product of the position vector (distance vector) and the force vector. Pressure measuring device pressure cell Rheology under pressure is used to simulate process conditions, to measure above the boiling point, or to prevent sample evaporation. The pressure cell specifications are therefore tailored to each application. In the petrochemical industries, high pressures of up to 1000 bar and temperatures of up to 300 °C are required, whereas work with low-viscosity solvents requires a sensitive, yet fully closed system. To cover these diverse applications, a range of different pressure cells and measuring systems is available. (7, — Diaphragm capsule Fig168 1 type Differential Pressure Transmitter Ultrasonic flow meter Principle Density is measured according to absorption method. A radioactive source (Cs-137) contained in a lead-shield, steel- enclosed housing is mounted on one side of pipe with a scintillation detector on the opposite side. Gamma energy emitted from the source passes through the pipe and the process material. The amount of energy reaching the detector changes with the density change of the material being measured. Density is determined based on energy attenuation and fluid concentration or solid content is calculated via density Measurement of temperature Temperature measurement, also known as thermometry, describes the process of measuring a current local temperature for immediate or later evaluation. Datasets consisting of repeated standardized measurements can be used to assess temperature trends 123 45 6 F 8 9 10 11 12 13 14 I il ll | ll J | pH In chemistry, pH (potential of hydrogen) is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per liter, of hydrogen ions. More precisely it is the negative of the base 10 logarithm of the activity of the hydrogen ion.Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, at pH 7 (25 °C), being neither an acid nor a base. Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. Measurements of pH are important in agronomy, medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment and water purification, and many other applications. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator Vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin vibrationem ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, such as the movement of a tire on a gravel road. Vibration can be desirable: for example, the motion of a tuning fork, the reed in a woodwind instrument or harmonica, a mobile phone, or the cone of a loudspeaker. In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations could be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. Careful designs usually minimize unwanted vibrations. The studies of sound and vibration are closely related. Sound, or pressure waves, are generated by vibrating structures (e.g. vocal cords); these pressure waves can also induce the vibration of structures (e.g. ear drum). Hence, attempts to reduce noise are often related to issues of vibration. The total instantaneous power absorbed by the three loads Z1, Z2 and Z3, are equal to the sum of the powers measured by the Two wattmeters, W1 and W2. Measurement of Power by Two Wattmeter Method in Star Connection Considering the above figure (A) in which Two Wattmeter W1 and W2 are connected, the instantaneous current through the current coil of Wattmeter, W1 is given by the equation shown below. Instantaneous potential difference across the potential coil of Wattmeter, W1 is given as Instantaneous power measured by the Wattmeter, W1 is Measurement of Power by Two Wattmeter Method in Delta Connection Considering the delta connected circuit shown in the figure below. The instantaneous current through the coil of the Wattmeter, W1 is given by the equation Instantaneous Power measured by the Wattmeter, W1 will be Therefore, the instantaneous power measured by the Wattmeter, W1 will be given as The instantaneous current through the current coil of the Wattmeter, W2 is given as The instantaneous potential difference across the potential coil of Wattmeter, W2 is Therefore, the instantaneous power measured by Wattmeter, W2 will be Hence, to obtain the total power measured by the Two Wattmeter the two equations, i.e. equation (3) and (4) has to be added Where P is the total power absorbed in the three loads at any instant The pressure coil of all the Three wattmeters namely W1, W2 and W3 are connected to a common terminal known as the neutral point. The product of the phase current and line voltage represents as phase power and is recorded by individual wattmeter. The total power in a Three wattmeter method of power measurement is given by the algebraic sum of the readings of Three wattmeters. i.e Where W1 = V1I1 W2 = V2I2 W3 = V3I3 Except for 3 phase, 4 wire unbalanced load, 3 phase power can be measured by using only Two Wattmeter Method