Transducers_1[1]

advertisement
Transducers/Sensors
• Transducer/sensor converts a nonelectrical 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
• 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
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
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
Transducers/Sensors
• Sensors generate analogue outputs such
as voltage or frequency
• Sensors generate digital outputs such as
pulses or digital data
Transducers/Sensors: Examples
• Linear displacement:
– Resistance
– Capacitance
– Electromagnetism LVDT (linear variable
displacement transformer)
– Ultrasonic
– Optical
– …………
Transducers/Sensors: Examples
• Temperature:
– Thermocouple
– Platinum resistance
– Thermistor
– Semiconductor junction
– Semiconductor thermometer
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. ???
Download
Related flashcards

Audio storage

18 cards

Digital audio

64 cards

Audio storage

25 cards

Audio engineering

43 cards

Audio effects

16 cards

Create Flashcards