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Slip ring | Advantages | Disadvantages | Application Hi guys here we learn about Slip ring and their advantage, disadvantages, and application of Slip ring. Also information about working and construction. Slip ring rotor — Fig a shows the construction of slip ring rotor. — The rotor winding is connected in the star connection like a normal three phase star connected transformer. — Fig. 7.4.1 (a) shows that alongwith the rotor drum, the motor shaft also carries three sliprings which are circular in shape and rotate at the same speed as that of the rotor. — The rotor winding terminals are permanently connected to these sliprings. The sliprings are continuously in contact with three brushes which are pressed against the sliprings using springs. — Many a times an external resistance is necessary to be connected in the rotor resistance. So a variable resistance is connected in the rotor winding. — Such an external resistance is essential to develop a...

Here we learn about Potentiometer | construction and working | Advantages and Disadvantages | Application and Types and Diagram. Potentiometer : 1) It is also called variable resistance device, A  potentiometer for measurement of linear motion or angular niotion is shown in Figs, 2,1,4 (a) and (b) ' respectively, This device is in fact a variable resistor whose resistance varies on account of movement of the  slider or wiper over a resistance element, 2) The wiper is connected to an arm and. the arm moves in a linear direction when the linear motion under  measurement is applied to it, 3) The same is applicable for the angular measurement,  Here Fig, 2,1,4 (a) shows the linear measurement, On account of the movement of the arm, the wiper moves over the resistance element. 4) Thus the resistance of the potentiometer is changed and the change in resistance isi a function of movement (displacement) applied to it. 5) The change in the value of resistance may be measured ...

Here we learn about piezoelectric transducers, with diagram and construction with working. Piezoelectric transducers : — Certain materials, when mechanically strained generate within them an electric charge. lhe effect is given the name of piezoelectric effect (pressure electricity). This effect is reversible, that is, if a charge is applied, the material deforms mechanically. Such materials, when subjected to alternating electric field, will expand and contract alternatively. — These materials fall into three main groups : Natural (quartz, Rochelle salt) and Synthetic (lithium sulphate, ammonium dihydrogen phosphate crystals) Polarized ferroelectric ceramics (barium titanate). — The desirable properties of piezoelectric materials, materials are stability, high output and ability to function under high temperature and humidity conditions, Quartz has high stability but low output. Rochelle salt has high output but requires protection from moisture. Barium titanate is commonly used in ul...

Here we learn about diaphragm and types of diaphragm, Advantage and Limitations of diaphragms with diagram Diaphragm : ~ The diaphragm is a thin member of sheet metal made to precise dimensions either in the shape of membrane or circular disc. If unknown pressure ig applied on one side of diaphragm, It gets deflected. The deflection of diaphragm is proportional to applied pressure. The measure of the leflection is the calibrated in terms of pressure. For pressure range 0 to 6.7 KPa membrane type liaphragm is used and for O to 350 KPa circular flexible disc type diaphragm is used.  Phosphor bronze, beryllium copper, brass, Teflon, Monel metal etc are used as diaphragm material. Slack diaphragms are made from non-metallic materials like animal membrane, Teflon polyether etc. Types of diaphragms: Depending upon strength and amount of deflection, the diaphragms are (a) Flat type diaphragm (b) Corrugated or disc type diaphragm If the diaphragm is made using pair of discs welded together...

Here we learn about thermocouples, application Laws for thermocouples, Law of intermediate metals, Law of intermediate temperature and Pettier effect. Thermocouples : ~ The basic principle of a thermocouple is that when two dissimilar metal wires are joined to form a completely electric circuit, and the two junctions are maintained at different temperatures, an electromotive force is setup.  due to the algebraic sum of an emf developed between two dissimilar metals placed in contact which is known as Seebeck effect Or an emf developed between the two ends of a homogeneous wire when one end is heated, which is called the Thomson effect. ~ The above principle is used to form thermocouples and to measure the high temperatures as in furnaces. In this, the junction, which is kept at hot source is called hot junction and the junction, at whom the emf produced is called cold junction. he magnitude of the emf depends oi the temperature difference of the junctions and the metals used. A sim...

Here we learn about thermocouple and construction of thermocouples, Thermocouple materials and Desirable properties thermocouples of materials Thermocouple Construction : ~ The thermocouple wires should be in electrical contract only at the hot junction, since contact at any other point will usually result in too low a measured emf cutting off. ~ Thermocouples are manufactured by suitable lengths of the two wires; the ends are carefully twisted together for about two turns, or sometimes butted together, and welded, brazed to form a smooth and rounded head. ~ A thermocouple consists of two pieces of dissimilar metals with their ends joined together (by twisting, soldering or welding). When heat° is applied to °the junction, a voĺtage, in the range of milli-volts (mV), is generated. A thermocouple is therefore said to be self- powered as shown in Fig. 3.5.3 is completed thermocouple circuit. ~ The voĺtage generated at each junction depends on junction temperature. If temperature T1 is hi...

Here we learn about optical pyrometer, advantages of optical pyrometer, disadvantages of optical pyrometer, also learn about Safety tools with images. Optical Pyrometer : ~ When radiation from heated body at high temperature falls within the visible region of electromagnetic spectrum. ~ An image of radiating source is produced by lens and made coincide with filament of lamp. ~ In optical pyrometer wavelength of radiation accepted is restricted by colour filter and its brightness is compared with standard lamp. ~ In an alternative approach, current through the lamp filament is maintained constant. ~ An optical wedge of absorbing material is moved up and down and its variable thickness accentuates the incoming energy to match the filament. ~ The wedge position is then calibrated for temperature. ~ The pyrometer is calibrated by sighting it upon a black body at various known temperature. ~ However if the temperature of filament is higher than that required for equal brightness, filament b...

Here we learn about hot wire anemometer, Hot Film anemometer, and it’s advantages and disadvantages. Hot wire Anemometer : ~ Hot wire anemometer is used for measurement of flow rate of fluctuating and unsteady flow. ~ A sensor of 5 micron diameter platinum tungsten wire welded between two prongs of the probe and heated electrically to form part of Wheatstone circuiit. ~ When the probe in introduced into the flowing fluid, it tends to be cooled by the velocity and there is decrease in its resistance. ~ The rate of cooling of wire depends upon the: (i) Dimension and physical properties of the wire. (ii) Difference of the temperature between the wire and fluid. (ii) Physical properties of the fluid. (iv) Stream velocity under measurement. ~ There are two methods of measuring fluid flow. Fig. Hot wire bridge circuits. 1. Constant-current mode : ~ Fig 4.3.1 (a) shows Constant-current mode hot wire anemometer in which the voltage across the bridge is kept constant. ~ Initially the circuit ad...

Here we learn about Sling psychrometer, and their advantages of sling psychrometer with fig., Hair hygrometer, recording psychrometer. A ) Sling psychrometer : ~ The sling psychrometer consists of handle of two mercury thermometers mounted on frame, which has handle provided for rotation of psychrometer as shown in Fig. 5.2.2. ~ For accurate measurement temperature, it is an essential condition that the air should move with velocity around the wet wick. ~ The sling psychrometer is a specific form of wet and dry bulb psychrometer. ~ It uses glass thermometers in a frame designed to be swing rapidly to obtain adequate air velocity. ~ This is suitable for measurement in the range of- 0 to 100 % RH. Fig. Sling psychrometer Applications of sling psychrometer : For setting and checking hair hydrometer. For routine meteorological observations. B) Hair hygrometer : ~ Hair hygrometer is the simplest and oldest type of hygrometer. ~ It is made using hair as shown in Fig. 5.2.1. ~ Human hair leng...

Here we learn about load cell, Definition of load cell, Advantages of load cell and Disadvantages of load cell, Application and types of load cell. Load Cell : Definition of load cell : Fig. Strain gauge load cell ~ Load cell is a force transducer which utilizes deflection of an elastic member as a primary sensing device and strain gauge as a secondary transducer. In hydraulic and pneumatic load cells, fluid pressure is used to measure the force.     Types of mechanical load cells : 1. Hydraulic load cell 2. Pneumatic load cell 3. Strain gauge load cell Applications of load cell : Tool dynamometers, weighing machines for vehicles, load measurement in material handling devices such as crane or AGV. Bag filling machines, suspension bridges etc. ~ Load cell is application of wire type bonded strain gauge. ~ It works on the principle of the elasticity i.e. when axial force is applied, its column gets compressed and when force is released it regains its original position. ~ Four wi...

Here we learn about Strain Gauge Rosettes with diagram Strain Gauge Rosettes ~ Multiple grid or rosettes are a group of gauges bonded to the same supporting material in definite relative positive. ~ When two 0r more grid elements are configured in a definite fashion for use at one point, then it is called a strain gauge rosette. In the use of a single element gauges, the orientation is a critical factor and are useful only in known directions. ~ But, with the use of strain gauge rosettes, there is no restriction on the orientation and can be used to measure stress whose magnitude and direction are totally unknown. ~ Theoretically, it is possible  calculate all the desired information when a 3-gauge rosette is used for measurement at a point. The different types of strain gauge rosettes are shown in Fig. 5.6.7. ~ Depending upon the arrangement of the grids, we have the rectangular, delta and T delta rosettes. Resistances Heating ~ When a resistance R carries a current I for t second...

Here we learn about Closed loop system, Definition, Advantages and disadvantages of closed loop system, Examples of closed Loop system. Closed Loop System Definition of closed Loop system : ~ A system in which the controlling action is some how dependent on the output is called as closed loop system. ~ Such system uses a feedback that is part of the output is feedback to the input and it is compared with the reference input. ~ Feedback is the property of the control system which allows the output to be compared with the reference input so that appropriate controlling action can be executed. ~ It is then compared with the reference input giving error signal e= R ± b. When feedback signal sign is positive, system is called as, positive feedback system (e = R+ b) and when feedback sign is negative system is called as negative feedback system (e= R-b). ~ This error is then manipulated by the controller generating manipulated actuating signal for the process to be controlled. This manipulat...

Servomotor Mechanism : ~ By servo-mechanism or simply a servo, we mean , system which is used to automatically control the output mechanical position, or time derivative of position, viz velocity or acceleration of the output member, in response to variations of input signal. ~ As such, a servo system is used to position a final control element in a generalized instrumentation system. ~ Servo-mechanism has found number of applications in industry, such as in tool position control, radar tracking systems, misslle guidance system etc. ~ Actuators are used to operate the final control element such as a valve, heater, etc. It is an important element of servo-mechanism.  A servo-mechanisin is a closed loop system that moves or changes the position of the controlled object so that it agrees with the position of a control device. In short servo may be considered, as any type of closed-loop system. ~ The error detector compares the feedback signal with the reference input or command and ge...