linear variable differential transducer.pptx

linear variable differential transducer

1. LINEAR VARIABLE DIFFERENTIAL TRANSDUCER (LVDT) Mohamed Ahmed Mohamed ID : NO B5en464

2. OUTLINE Introduction Types of LVDT Construction of LVDT Working principle of LVDT Application of LVDT Advantages Disadvantages

3. LVDT works under the principle of mutual induction, and the displacement which is a nonelectrical energy is converted into an electrical energy. It is also called as LINEAR VARIABLE DIFFERENTIAL TRAN SDUCER Introduction

4. Captive Armature LVDT Unguided Armatures Force Extended Armatures Captive Armature LVDT These types of LVDTs are superior for lengthy working series. This LVDTs help to prevent incorrect arrangement because they are directed and controlled by low resistance assemblies. Unguided Armatures LVDT These types of LVDTs have unlimited resolution behavior, the mechanism of this type of LVDT is a no-wear plan that doesn’t control the motion of calculated data. This LVDT is connected to the sample to be calculated, fitting limply in the cylinder, involving the linear transducer’s body to be held independently. Types of LVDT

5. Unguided Armatures LVDT These types of LVDTs have unlimited resolution behavior, the mechanism of this type of LVDT is a no-wear plan that doesn’t control the motion of calculated data. This LVDT is connected to the sample to be calculated, fitting limply in the cylinder, involving the linear transducer’s body to be held independently. Cont …

6. Unguided Armatures LVDT These types of LVDTs have unlimited resolution behavior, the mechanism of this type of LVDT is a no-wear plan that doesn’t control the motion of calculated data. This LVDT is connected to the sample to be calculated, fitting limply in the cylinder, involving the linear transducer’s body to be held independently. Cont …

7. Construction of LVDT L VDT c o n sists o f a cy l in d r i cal T r an s f or m e r where it is surrounded by o n e pr i m ar y winding in the cen t r e o f t h e transformer and the two secondary windings at the sides. The number of turns in both the secondary windings are equal, but they are opposite to each other. The Primary Winding is Connected to an ac source. A movable soft iron slides within the hollow former and therefore affects the magnetic coupling between the primary and the two secondaries

8. Working of LVDT: The Displacement to be Measured is applied to an arm attached to the Soft iron core

9. Case 1: When the Core is in its normal position. Equal Voltages induced in the two secondary windings The Output Voltage of secondary winding S 1 is E s1 and secondary winding S 2 is E s2 The Differential output Voltage E =E S1 ~E S2 At Normal Position E =0 ,because The Flux linking with both secondary windings is equal , hence equal emf are induced in them. (i.e E S1 =E S2 )

10. Case 2: When the Core is moved to the left of null position Now, if the core is moved to the left of the null position, more flux links with winding S₁ and less with winding S2. Hence, output voltage Es, of the second- ary winding S₁ is greater than Es,. The magnitude of the output voltage of the secondary is then Es, - Es,, in phase with Es, (the output voltage of secondary winding S₁).

11. Case 3: When the Core is moved to the right of null position if the core is moved to the right of the null position, the flux linking with winding S₂ becomes greater than that linked with winding S₁. This results in Es, becoming larger than Es. The output voltage in this case is E, Es, - Es, and is in phase with Es

12. Cont … The amount of voltage change in either secondary winding is propotional to the amount of movement of the core The amount of output voltage may be measured to determine displacement. The output signal may also be applied to a recorder or to a controller that can restore the moving system to its normal position. The output voltage of a LVDT is a linear function of the core displacement within a limited range motion (say 5mm from null position)

13. Con t … The Characteristics are linear from O-A and O-B , But after that they become non-linear. LVDTs are available with ranges as low as ± 0.05 in. to as high as ± 25 in. and are sensitive enough to be used to measure displacements of well below 0.001 in. They can be obtained for operation at temperatures as low as - 265°C and as high as + 600°C and are also available in radiation resistance designs for nuclear operations.

14. Advantages of LVDT 1. Linearity The output voltage of this transducer is practically linear for displacements upto 5 mm (a linearity of 0.05% is available in commercial LVDTs). 2. Infinite resolution The change in output voltage is stepless. The effective resolution depends more on the test equipment than on the transducer. 3. High output It gives a high output (therefore there is frequently no need for intermediate amplification devices). 4. High sensitivity The transducer possesses a sensitivity as high as 40 V/mm. 5. Ruggedness These transducers can usually tolerate a high degree of vibration and shock. 6. Less friction There are no sliding contacts.

15. Advantages of LVDT Frictional loss reduced: Since the iron core does not have contact with the transformer coil there is no friction between them and the chances of frictional losses are reduced which makes LVDT the best device. If there will be no friction then there will also be no wear and tear in the object. Power consumption is low: During operation, there are many times when the power required to operate the machine is low as LVDT uses only 1W power to operate. Therefore the power consumption is low. Uneven operational shock: It can tolerate a high proportion of shock and vibration especially when a core is loaded with a spring. This makes LVDT the best transducer. Because of their small size and lightweight, they are stable and aligned.

16. Disadvantages of LVDT Large displacements are required for differential output. They are sensitive to stray magnetic field (but shielding ids possible). The receiving instrument must be selected to operate on ac signals, or a demodulator network must be used if a dc output is required. The dynamic response is limited mechanically by the mass of the core and electricity by applied voltage. Temperature also affects the transducer.

17. Disadvantages of LVDT Large displacements are required for differential output. They are sensitive to stray magnetic field (but shielding ids possible). The receiving instrument must be selected to operate on ac signals, or a demodulator network must be used if a dc output is required. The dynamic response is limited mechanically by the mass of the core and electricity by applied voltage. Temperature also affects the transducer.

18. Cont … Affected by various factors: Vibration, variation, and temperature are a few factors that affect the working of LVDT. As it is an electromagnetic device it has to be affected by these factors. Large displacement for small output: LVDT has to measure a large number of displacements to provide a small output that is one of the demerits of LVDT. Use of demodulator: since LVDT is an AC signal thus we have to use a demodulator network to obtain DC output. This is again one of the demerits of LVDT.

19. Applications of LVDT Acting as a secondary transducer, LVDT can be used as a device to measure force, weight and pressure, etc.. Testing of soil strength PILL making Machine “Brain Probing” medical device Robotic Cleaner Dollar bill thickness in ATM Machine. Hydraulic cylinder Displacement.