Sensors & Transducers: Advantage & disadvantage Unit 1 Part 3

Que1.18. Explain the construction and working of  optic encoder  for  relegation  dimension with suitable  illustration. 

Answer  1. An  optic encoder is an electromechanical device which has an electrical  affair in digital form commensurable to the angular position of the input  shaft.  2. optic encoders enable an angular  relegation to be converted directly  into a digital form. An  optic encoder is an angular position detector.  3. It has a shaft mechanically coupled to an input  motorist which rotates a  slice  strictly fixed to it.  4. Light from infrared emitting diodes reaches the infrared receivers  through the transparent gashes of the rotating slice.  5. also electronically, the signal is amplified and converted into digital  form. This signal is  also transmitted to the data processor.  6. It comprises of a slice with three concentric tracks of inversely spaced  holes.  7. Three light detectors are employed to  descry the light passing through the  holes.  8. These detectors produce electric  beats which give the angular   relegation of the mechanical elemente.g. shaft on which the  optic  encoder is mounted. 1.18.1. Construction and working of  optic encoder.  9. The inner track has just one hole which is used  detect the’ home’ position  of the slice. The holes on the middle track  neutralize from the holes of the   external track by one- half of the  range of the hole. This arrangement  provides the direction of gyration to be determined.  10. When the slice rotates in clockwise direction, the  beats in the  external  track lead those in the inner; in counter clockwise direction they lag  before.  11. The resolution can be determined by the number of holes on slice. With  100 holes in one revolution, the resolution would be,  °/ 100 = 3.6 °  

Que1.19. What are  cargo cells? What are its types? 

Answer  cargo cell A  cargo cell is a force hand that consists of a transducer that  is used to  produce an electrical signal whose magnitude is directly  commensurable to the force being measured.  Types  Curvaceous  Hydraulic  Strain hand  Piezoresistive  Magnetostrictive.   

Que1.20. What’s strain hand? Give its principle. 

Answer  1. Strain hand  cargo cells are a type of  cargo cell where a strain hand  assembly is  deposited inside the  cargo cell  casing to convert the  cargo  amusement on them into electrical signals.  2. The weight on the  cargo cell is measured by the voltage change caused  in the strain hand when it undergoes  distortion.  3. The resistance of a strain hand varies with applied force and, it converts  parameters  similar as force, pressure, pressure, weight,etc. into a change  in resistance that can be measured  latterly on.  4. Whenever an external force is applied to an object, it tends to change its  shape and size thereby, altering its resistance.  5. The stress is the internal resisting capacity of an object while a strain is  the  quantum of  distortion endured by it.  6. Any  introductory strain hand consists of an  separating flexible backing that  supports a metallic antipode pattern.  7. The hand is attached to the object under stress using an  glue. The   distortion in the object causes the antipode to get distorted which eventually  changes the electrical resistivity of the antipode.  8. This change in resistivity is measured by a Wheatstone ground which is  affiliated to strain by a  volume called, hand factor.  9. A strain hand works on the principle of electrical conductance and its  dependence on the captain’s  figure.  10. Whenever a captain is stretched within the limits of its pliantness, it  does n’t break but, gets narrower and longer.  11. also, when it’s compressed, it gets shorter and broader, eventually  changing its resistance.  

Que1.21. How do you measure strain with a strain hand? 

Answer  1. Strain gauges work on the principle of the captain’s resistance which  gives you the value of hand factor by the formula  Hand factor( GF) = ( R/( RG *)) 

2. Now, the change in the strain of an object is a  veritably small  volume which  can only be measured using a Wheatstone ground. 

3. A Wheatstone ground is a network of four resistors with an excitation  voltage, VEX that’s applied across the ground. The Wheatstone ground is  the electrical  fellow of two  resemblant voltage  separator circuits with R1  and R2 as one of them and R3 and R4 as the other bone.

4. The affair of the Wheatstone circuit is given by  VO = (( R3/ R3 R4) –( R2/ R1 R2)) × VEX.(1.21.1)  5. Whenever R1/ R2 =  R4/ R3, the affair voltage VO is zero and the ground is  said to be balanced. Any change in the values of R1, R2, R3, and R4 will,   thus, change the affair voltage.  6. still, indeed a minor change  If you replace the R4 resistor with a its resistance will change the affair voltage VEX which is a function  of strain. 

7. The original strain affair and voltage affair always have a relation  of 2 1. 

8. In a  cargo cell, these resistors are replaced by strain needles in interspersing  pressure and  contraction  measures. When a force is applied to the   cargo cell, the resistance in each strain hand changes and VO is measured. 

9. From the performing data, VO can be  fluently determined using the  eq.(1.21.1).  

Que1.22. Explain the characteristics of strain needles. 

Answer  1. They’re  largely precise and do not get  told  due to temperature  changes. still, if they do get affected by temperature changes, a  thermistor is available for temperature corrections. 

2. They’re ideal for long distance communication as the affair is an  electrical signal. 

3. Strain needles bear easy  conservation and have a long operating life.  4. The  product of strain needles is easy because of the simple operating  principle and a small number of  factors. 

5. The strain needles are suitable for long- term installation. still, they  bear certain  preventives while installing. 

6. All the strain needles are hermetically sealed and made up of  pristine   sword  therefore, leakproof.  7. They’re completely  reprised for protection against  running and  installation damage.  8. The remote digital readout for strain needles is also possible.   

Que1.23. Give the  operations of strain needles. 

Answer  1. Strain needles are extensively used in experimental stress analysis and   opinion on machines and failure analysis. 

2. They’re  principally used formulti-axial stress fatigue testing,  evidence testing,  residual stress and vibration  dimension, necklace  dimension,  bending and  deviation  dimension,  contraction and pressure   dimension and strain  dimension. 

3. Strain needles are primarily used as detectors for machine tools and safety  in automotive. 

4. In particular, they’re employed for force  dimension in machine  tools, hydraulic or curvaceous  press and as impact detectors in aerospace  vehicles.  

Que1.24. Explain the working of LVDT grounded diaphragm pressure  detector. 

Answer  1. The diaphragm pressure hand uses the elastic  distortion of diaphragm  i.e. membrane)  rather of a liquid  position to measure the difference  between the unknown pressure and a reference pressure. 

2. A typical diaphragm pressure hand contains a capsule divided by a  diaphragm, as shown

3. One side of diaphragm is open to the external targeted pressure,PExt.,  and the other side is connected to a given pressure, PRef. The pressure  difference PExt – PRef, mechanically deflects the diaphragm. 

4. The membrane of the diaphragm is connected to LVDT as shown in 1.24.2. 

5. Due to  operation of pressure on diaphragm, a  relegation is applied  on core or primary winding of LVDT. As a result a voltage is  convinced in  the secondary winding of LVDT. This  convinced voltage is directly  commensurable to applied pressure.

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