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Transducers/Sensors

Transducers/Sensors. Transducer/sensor converts a non-electrical quantity, measurand, into a related electrical output signal Ideally there is a linear relationship between the measurand and the output Sensors often need a source of energisation, a power supply. Transducers/Sensors.

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Transducers/Sensors

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  1. Transducers/Sensors • Transducer/sensor converts a non-electrical quantity, measurand, into a related electrical output signal • Ideally there is a linear relationship between the measurand and the output • Sensors often need a source of energisation, a power supply

  2. Transducers/Sensors • What’s the measurement made for? • Information, to quantify the measurand • Record, to provide a historical profile • Control, use the information to control some process • Sensor measurements are subject to errors • Noise • cross sensitivity, output changes because it’s sensitive to other environmental variables • Characteristic errors, deviation from the predicted response • Dynamic errors, non-ideal frequency or time response

  3. Transducers/Sensors • Important Characteristics • Accuracy, usually expressed in %, variation from the stated linear (or other relationship) between measurand and output • Resolution, smallest change in the measurand that can be detected in the output • Range, range of value of the measurand that the sensor can accurately sense

  4. Transducers/Sensors • For any form of measurand there are always several sensors that can be used, which one depends on the application • Similarly, many sensors can be used to sense different measurands • E.g: Temperature: thermocouple, resistance thermometer, thermistor, semiconductor sensor, infra-red thermometer…… • E.g: Strain gauge: strain, pressure, height, displacement, velocity, acceleration

  5. Transducers/Sensors • Sensors generate analogue outputs such as voltage or frequency • Sensors generate digital outputs such as pulses or digital data

  6. Transducers/Sensors: Examples • Linear displacement: • Resistance • Capacitance • Electromagnetism LVDT (linear variable displacement transformer) • Ultrasonic • Optical • …………

  7. Transducers/Sensors: Examples • Temperature: • Thermocouple • Platinum resistance • Thermistor • Semiconductor junction • Semiconductor thermometer

  8. Transducers/Sensors: Exercise • Use the rest of the lecture time for a web search on the transducer type given: 1. Range of types available & typical devices (diagrams, photos?) 2. Accuracy, range, resolution 3. Measurand/output law (linear?, shown as a graph?, other?) 4. Cross-sensitivity? Other important electrical characteristics 5. ???

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