Page 400 - Sensors and Control Systems in Manufacturing

354
Cha p te r
Se v e n

Optoelectronic Oil tank
instrument
Light source Optical fiber

Accident
detector

Oil tanks
Detector
Alarm
system

x Liquid - level sensor

Computer
(a)

Deflected beams Undeflected beams
Green

Red
Green
Water Steam
Red

Red
Steam
Red

Green

Water Green
Red
Green
Red
Green
Green
Green
(b)
FIGURE 7.35 (a) Principle of operation of a liquid level sensor for the
measurement of boiler-drum water. (b) Liquid level sensor for the
measurement of boiler-drum water with fi ve-port sensors.