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Pharos University

Pharos University. EE212_ELECTRICAL MEASUREMENT & Interface Prepared By: Dr. Sahar Abd El Moneim Moussa. Ch6_ SENSORS & TRANSDUCERS. SENSORS & TRANSDUCERS Introduction: A transducer is any device that converts energy from one form to another .

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Pharos University

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  1. Pharos University EE212_ELECTRICAL MEASUREMENT & Interface Prepared By: Dr. SaharAbd El MoneimMoussa Dr. SaharAbd El MoneimMoussa

  2. Ch6_ SENSORS & TRANSDUCERS Dr. Sahar Abd El Moneim Moussa

  3. SENSORS & TRANSDUCERS Introduction: • A transducer is any device that converts energy from one form to another. • The input quantity for most instrumentation system is non-electrical. In order to use electrical measuring instrument, the non-electrical quantity is converted into an electrical signal by a suitable transducer. Dr. SaharAbd El MoneimMoussa

  4. I- Displacement measurement 1- Linear Potential Transducer: • In this circuit, the moving system (to measure its displacement) is linked with the sliding contact on the resistor. • A change in position, causes a change in the resistance of the potentiometer, acting as a relative position transducer, and consequently a change in the currentand the output voltage. Dr. SaharAbd El MoneimMoussa

  5. Dr. Sahar Abd El Moneim Moussa

  6. Example (1): Dr. Sahar Abd El Moneim Moussa

  7. Solution: Dr. Sahar Abd El Moneim Moussa

  8. Example (2): Dr. Sahar Abd El Moneim Moussa

  9. Solution: Dr. Sahar Abd El Moneim Moussa

  10. 2- Rotary Potential Transducer: Dr. SaharAbd El MoneimMoussa

  11. Example (3): Dr. Sahar Abd El Moneim Moussa

  12. Solution: Dr. Sahar Abd El Moneim Moussa

  13. Dr. Sahar Abd El Moneim Moussa

  14. 2- Strain Measurement Strain Gauge: • A strain gauge is a resistance-changing transducer. It consists of a fine wire looped back and forth many times and bonded to the face of a mounting plate. • Strain gauges uses the electrical resistance variation in the wire to sense the strain produced by any force on the wire. • It is used to measure weight, pressure, and mechanical force . Dr. SaharAbd El MoneimMoussa

  15. Strain Gauge: (cont.) Therefore, Where, E: Young’s Modulus of the wire material, Kg/m2 Dr. SaharAbd El MoneimMoussa

  16. When we apply a force a wire, there will be change in the wire length as well as its width. Dr. SaharAbd El MoneimMoussa

  17. Dr. SaharAbd El MoneimMoussa

  18. Since, • Therefore, the change in the resistance due to the applied strain will be, • The change in the resistance will be, 0 Change in the Resistance Change in the Area Change in the Length Change in the Resistivity Dr. SaharAbd El MoneimMoussa

  19. Therefore Poisson ratio will be, • Accordingly, the change in the resistance will be, Dr. SaharAbd El MoneimMoussa

  20. The Gauge factor is the relation between the change in the resistance with respect to the strain. 1 + 2 Dr. SaharAbd El MoneimMoussa

  21. Example (4): Solution: Dr. Sahar Abd El Moneim Moussa

  22. 3- Temperature Measurement a- Resistance Temperature Detector: (RTD) Dr. SaharAbd El MoneimMoussa

  23. The relation between the resistance and the temperature can be approximated to a linear equation as follows: Dr. SaharAbd El MoneimMoussa

  24. Example (5): Dr. Sahar Abd El Moneim Moussa

  25. Solution: Dr. Sahar Abd El Moneim Moussa

  26. b- Thermistor: • In this type the resistance element is semiconductor. • As temperature increase, the resistance decreases Dr. SaharAbd El MoneimMoussa

  27. Dr. SaharAbd El MoneimMoussa

  28. Example (6): Dr. Sahar Abd El Moneim Moussa

  29. Dr. Sahar Abd El Moneim Moussa

  30. Solution: Dr. Sahar Abd El Moneim Moussa

  31. Example (7): Dr. Sahar Abd El Moneim Moussa

  32. Solution: Dr. Sahar Abd El Moneim Moussa

  33. Dr. Sahar Abd El Moneim Moussa

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