Mechanical Transducers

The Presentation is on the Transducers and some daily used transducers used in our life.

1. transducers A presentation by mahak pandya 19bme066 Mechanical measurements and meteorology Submitted to : krunal mehta sir

2. transducers Transducers are device which converts one form of energy to another. Usually they convert a signal in one form of energy to a signal in another. Basically, they are used in automation, measurement and control systems where electrical signals are converted to other signals. Hence, it can convert any quantity to be measured into a usable electrical signals. These are used by us in our daily life. Examples are Microphone, Loudspeakers, Thermometers, Antennae etc.

3. More about transducers… Transducer has basically two parts Sensing Element Transduction Element Sensing Element : the part which gives response to the physical sensation. Its response depends on the physical phenomenon. Transduction Element : it converts the output of sensing element into an electrical signal. Also known as “Secondary transducer”.

4. LET US DISCUSS FOUR MECHANICAL TRANSDUCERS USED IN DAILY SCIENCE!!

5. 1. bimetallic strip A   bimetallic strip  is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled.

6. T he working of the bimetallic strip depends on the thermal expansion property of the metal.  The thermal expansion is the tendency of metal in which the volume of metal changes with the variation in temperature . Every metal has a different temperature coefficient. The temperature coefficient shows the relation between the change in the physical dimension of metal and the temperature that causes it. The expansion or contraction of metal depends on the temperature coefficient, i.e., at the same temperature the metals have different changes in the physical dimension. Bimetallic strip construction

7. Principle The strip consists of two strips of different metals which expand at different rates as they are heated, usually  steel and  copper, or in some cases steel and brass. The strips are joined together throughout their length by riveting,  brazing or  welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The sideways displacement of the strip is much larger than the small lengthways expansion in either of the two metals. In some applications the bimetal strip is used in the flat form. In others, it is wrapped into a coil for compactness. The greater length of the coiled version gives improved sensitivity.

8. Working of the strip A traditional thermostat has two pieces of different metals bolted together to form what's called a  bimetallic strip  (or bimetal strip). The strip works as a bridge in an electrical circuit connected to your heating system. Normally the "bridge is down", the strip carries electricity through the circuit, and the heating is on. When the strip gets hot, one of the metals expands more than the other so the whole strip bends very slightly. Eventually, it bends so much that it breaks open the circuit. The "bridge is up", the electricity instantly switches off, the heating cuts out, and the room starts to cool.

9. Application of bimetallic strip Temperature indication Bimetals are used for temperature indication as in the spiral or helix actuated pointer thermometers. Such thermometers help measure temperatures in offices, refrigerators, and even on aircraft wings. Temperature control Bimetals are utilized as a means to control the temperature, as in room temperature thermostats. In such devices, a bimetal blade holds a current-carrying contact point that is linked to a coupled static contact point . Tube and pipe couplings For cryogenic, non-magnetic, and nuclear applications where metal properties must be switched reliably, bimetallic couplings are used to enable direct connection and transition for pipes and tubes with different CTEs. Function Control By introducing heat to a bimetal – or what is known as auxiliary heating – the function of a device containing the bimetal can be controlled. Circuit breakers and time delay devices are examples of these devices.

10. Bimetallic strip used in thermometers

11. 2. manometer A manometer is a scientific instrument used to measure gas pressures. Open manometers measure gas pressure relative to atmospheric pressure. A mercury or oil manometer measures gas pressure as the height of a fluid column of mercury or oil that the gas sample supports.

12. Construction of manometer Attach the plastic tubing carefully around the length of the plank using the tube fasteners. Ensure the tubing makes a smooth, even “U” bend around the end of the plank so that the tubing does not become kinked. Position the plank against a vertical surface, such as a board. Use the plumb bob to ensure the plank is exactly vertical. Hammer a nail through the plank or use some other means to attach it securely to the board . Pour approximately 100 ml water into the beaker. Add enough dye to turn the water a bright red and mix thoroughly. Pour the water carefully into the tube. Place a measuring device on the side of the manometer on the opposite end of the expected pressure. Line up the zero point of the measuring device with the surface of the liquid and attach it securely with tape. The measuring device may be a ruler or graph paper, depending on the specific application. Attach a source of positive pressure to one end of the manometer with an airtight seal. The pressure may then be measured in inches of water.

13. WORKING PRINCIPLE A manometer works on the principle of hydrostatic equilibrium and is used for measuring the pressure (static pressure) exerted by a still liquid or gas. Hydrostatic equilibrium states that the pressure at any point in a fluid at rest is equal, and its value is just the weight of the overlying fluid.

14. Working of manometer In a closed manometer, a sample of gas is introduced into one end, which is then capped. Then, a fluid of known density is poured into the other end. The fluid will stop moving when the pressure of the gas trapped between the cap and the fluid together with the pressure at the bottom of the fluid column on that side matches the pressure of air plus the pressure of the fluid column on the open side. The height of the fluid on the open side will be  higher  on that side when air pressure is less than the gas pressure and  lower  on the open side when the air pressure exceeds the gas pressure. You can use this height difference to calculate the gas pressure. Since P = F/A = mg/A, m = ρV and V = Ah for a cylindrical tube (i.e., volume = area times height), it can be shown that the pressure created by a vertical column of fluid is ρgh , where h = height in meters. This pressure represents the positive or negative difference between the gas pressure and atmospheric pressure.

15. Application of manometer It is used for low range pressure measurements. Extensively used in laboratories. Is used in Orifice meter and Venturimeter for flow measurements. It is used for calibration of gauges and other instruments. It is used for measuring pressure drop in different joints and valves.

16. A real manometer The Manometer Diagram

17. 3. gyroscope A  gyroscope   is a device used for measuring or maintaining orientation and angular velocity .  It is a spinning wheel or disc in which the axis of rotation (spin axis) is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum. Gyroscopes based on other operating principles also exist, such as the microchip-packaged MEMS gyroscopes found in electronic devices (sometimes called  gyrometers ), solid-state ring lasers ,  fibre optic gyroscopes , and the extremely sensitive quantum gyroscope .

18. Construction of gyroscope The gyroscope consists of a central wheel or rotor that is mounted in a framework of rings. The rings are properly called gimbals, or gimbal rings. Gimbals are devices that support a wheel or other structure but allow it to move freely. The rings themselves are supported on a spindle or axis at one end that, in turn, can be mounted on a base or inside an instrument. The property of the rotor axle to point toward its original orientation in space is called gyroscopic inertia; inertia is simply the property of a moving object to keep moving until it is stopped. Friction against the air eventually slows the gyroscope's wheel, so its momentum erodes away. The axle then begins to wobble. To maintain its inertia, a gyroscope must spin at a high speed, and its mass must be concentrated toward the rim of the wheel.

19. WORKING PRINCIPLE The basic effect upon which a gyroscope relies is that an isolated spinning mass tends to keep its angular position with respect to an inertial reference frame, and, when a constant external torque (respectively, a constant angular speed) is applied to the mass, its rotation axis undergoes a precession motion at a constant angular speed (respectively, with a constant output torque), in a direction that is normal to the direction of the applied torque (respectively, to the constant angular speed) . External forces acting on the center of mass of the rotating part do not affect the angular position of the rotation axis.

20. Working of gyroscope When the force is applied to the axle, the section at the top of the gyroscope will try to move to the left, and the section at the bottom of the gyroscope will try to move to the right, as shown. If the gyroscope is not spinning, then the wheel flops over, as shown in the video on the previous page. If the gyroscope is spinning, think about what happens to these two sections of the gyroscope:  Newton's first law of motion  states that a body in motion continues to move at a constant speed along a straight line unless acted upon by an unbalanced force. So the top point on the gyroscope is acted on by the force applied to the axle and begins to move toward the left. It continues trying to move leftward because of Newton's first law of motion, but the gyro's spinning rotates it. This effect is the cause of precession. The different sections of the gyroscope receive forces at one point but then rotate to new positions! When the section at the top of the gyro rotates 90 degrees to the side, it continues in its desire to move to the left. The same holds true for the section at the bottom -- it rotates 90 degrees to the side and it continues in its desire to move to the right. These forces rotate the wheel in the precession direction. As the identified points continue to rotate 90 more degrees, their original motions are cancelled. So the gyroscope's axle hangs in the air and precesses.

21. Application of gyroscope Gyroscopes are used in compasses and  automatic pilots on ships and aircraft, in the steering mechanisms of torpedoes, and in the inertial guidance systems installed in space launch vehicles, ballistic missiles, and orbiting  satellites.

22. GYROSCOPE GYROSCOPE SENSORS USED IN MOBILE

23. 4. Spring balance Spring balances provide a method of mass measurement that is both simple and cheap. The mass is hung on the end of a spring, and the deflection of the spring due to the downwards gravitational force on the mass is measured against a scale. Because the characteristics of the spring are very susceptible to environmental changes, measurement accuracy is usually relatively poor. However, if compensation is made for the changes in spring characteristics, then a measurement inaccuracy less than ±0.2% is achievable. According to the design of the instrument, masses between 0.5 kg and 10 tonne can be measured.

24. Construction of spring balance Spring balance is a weighing device that utilizes the relation between the applied load and the deformation of a spring. This relationship is usually linear;  i.e.,  if the load is doubled, the deformation is doubled. In the circular  balance, the upper ends of the helical springs are attached to the casing and the lower ends to a crossbar that can move relative to the casing and to which the load hook is attached. The pinion to which the indicating pointer is attached is pivoted in the casing and meshes with the rack, which is pivotally connected to the crossbar and is pressed into contact with the pinion by the rack spring . When a load is applied, the springs are stretched, and movement of the crossbar with the rack attached rotates the pinion and the load-indicating pointer. The dial is graduated in scale units that depend on the stiffness of the springs: the stiffer springs have larger scale units and higher load capacity.

25. working principle A spring scale or spring balance or Newton meter is a type of weighing scale. It consists of spring fixed at one end with a hook to attach an object at the other. It works by Hooke’s Law, which states that the force needed to extend a spring is proportional to the distance that spring is extended from its rest position. Hooke's law  states that the applied force  F  equals a constant k times the displacement or change in length x, or  F  =  kx . The value of k depends not only on the kind of elastic material under consideration but also on its dimensions and shape

26. Working of spring balance There is a direct relationship between how much the spring extends and the force required to extend it . If we place a weight at the end of the spring there is a force applied to the spring due to the weight. Hooke’s law says that the spring will then extend. As it extends you can measure the force due to the weight by looking at the scale. The spring extension and force applied is indicated on the scale .  a process of applying various forces to it and measuring the amount it extends for each unit of force. This enables us to calibrate it and create a scale which indicates force. 

27. Application of spring balance Main uses of spring balances are to weigh heavy loads such as trucks, storage silos, and material carried on a conveyor belt . They are also common in science education as basic accelerators. They are used when the accuracy afforded by other types of scales can be sacrificed for simplicity, cheapness, and robustness.

28. SPRING BALANCE USED IN LABS SPRING BALANCE USED IN CONVEYOR BELTS TO JOIN

29. THANK YOU !!!