1. ENT 164/4 SENSORS & MEASUREMENT
Shazmin Aniza Abdul Shukor

2. Measurement Reference books:
Theory and Design for Mechanical Measurements, Richard S. Figliola & Donald E. Beasley, John Wiley & Sons
Mechanical Measurements, Thomas G. Beckwith, Roy D. Marangoni, John H. Lienhard V, Pearson International Edition
Process Control Instrumentation Technology, Curtis D. Johnson, Pearson International Edition

3. General Measurement System (1)
Measurement = act of assigning a specific value to a physical variable (tool used for quantifying the measured variable)

4. General Measurement System (2)
Sensor = a physical element – employs natural phenomenon – senses the variable being measured
Transducer = converts sensed information – detectable signal (electrical, mechanical, optical, etc)
Signal conditioning = convert transducer signal – desired magnitude
Output = indicates / records value measured
Feedback-control = interprets measured signal; makes decision

5. General Measurement System (3)

6. Important Terms in Measurement (1)
Variables = entities that influence the test
Independent variable = changed independently of other variables
Dependent variable = affected by changes in one / more variables
Extraneous variables = cannot be controlled during measurement, but affect the value of variable measured

7. Important Terms in Measurement (2)

8. Important Terms in Measurement (3)
Parameter = a functional grouping of variables
Noise = random variation of the value of the measured signal as a consequence of the variation of the extraneous variables
Calibration = applies a known input value to a measurement system for the purpose of observing the output

9. Important Terms in Measurement (4)
Accuracy = closeness of agreement between the measured value and the true value
Error = difference between the measured value and the true value

10. Standards = reference value
Dimension = physical variable – describe aspect of physical system
Unit = quantitative measure of a dimension
E.g. mass (kg), time (s), length (m), temperature (K), current (A)
Derived units = association of dimensions and their units

12. Problem Identify the measurement stages for a room thermostat Answer:
Sensor / transducer stage: Bimetallic thermometer
Output stage: Displacement of thermometer tip
Controller: Mercury contact switch

13. mercury switch attached
Room Thermostat
Thermometer coil with
mercury switch attached
The mercury switch