Sensor - The Electronic Nose Artificial Olfaction Technology - page 32

Table 2.1 Sensor technology classification by measurand category [ 2 ]
Measurand/input
variable

Sensor/transducer
technology

Sensing subsystem mechanism Applications

Mechanical quantities
Linear position Encoders (optical) M-M. Optical probe—pin

photodiode

Industrial robots, machine tools

Angular position Resolvers (magnetic) M-C. AC magnetic probe-coil Manufacturing, process control

Position Potentiometer (variable voltage divider) C-M. Work done on wiper—

voltage probe

Automobile gas pedal, throttle valve

LVDT—linear variable differential
transformer

M-C. AC magnetic probe—coil Automotive, aerospace, manufacturing

Variable reluctance M-C. AC magnetic probe—coil Angular position

Direction (navigation) Mechanical Gyros M-M. Angular momentum—

capacitance

Inertial reference systems

Speed and RPM Tachometer C. Mechanical to electrical

(magnetic induction)

Frequency and amplitude proportional to RPM

Hall (based on pulse counting) M-M. Magnetic field—Hall effect Automotive ABS, ignition timing

Force (weight) Foil strain gauge C-PM. Work done against

gravity—electrical resistivity

Load cell is analogous to diaphragm in pressure
transducer

Pressure/differential
pressure

Capacitive C-M. Work on diaphragm—AC

probe

Built-in over-pressure protection

Silicon piezo-resistive bridge C-PM. Work on diaphragm—DC

resistive probe

MEMS-based

Foil strain gauge C-PM. Work on diaphragm—DC

resistive probe

Constantan (copper nickel alloy) foil

Level Float C-M. Liquid does work on the

float

Level measurement

Ultrasonic Ultrasonic, radar, laser beam

probes

Level measurement

Fiber optic in liquid M-M. Optical probe—photodiode used for temperature sensing