1. Arijit Sen Faculty Department of Mechanical Engineering IUBAT
Mec 337 Chapter - 6
Arijit Sen
Faculty
Department of Mechanical Engineering
IUBAT

2. Sensor
Iout = f(Iin)
Transfer efficiency = Iout /Iin
η = dIout /dIin

3. Loading of the Signal Source
Energy will always be taken from the signal source by the measuring system, which means that the information source will always be changed by the act of measurement. This is a measurement axiom. This effect is referred to as loading the smaller the load placed on the signal source by the measuring system, the better.

4. Classification of First Stage device
Class I: first stage elements used as detectors only
Class II: first stage elements used as detector and single transducer
Class III: first stage elements used as detector with two transducer.

5. Advantage of electrical transducer
Amplification or attenuation can be easily obtained
Mass inertia effects are minimized
An output power of almost any magnitude can be provided
Remote indication or recording can be feasible.
The transducer can often be miniaturized.

6. Variable resistance transducer element
R= ρL/A

7. Piezoelectric Sensor
Certain materials can generate an electrical charge when subject to mechanical strain or, conversely, can change their shape when subject to voltage. This is known as piezoelectric effect.
Vo(t) = Q(t)/Ct
Vo = Ghσ
Where G is a material constant, h thickness and σ is stress.

8. Light Detecting Transducer
Photoemissive detector
Photoconductive cell
Photovoltaic Cell
Photodiode