Welding Sensor Devices

Written by Frederick Eckart and Michael Francoeur

Sensors are devices that monitor changes or variations in an object or process relative to a reference standard.  Depending on their intended function, they can recognize changes in weight, vibration, motion, pressure, color, heat, light, magnetism or chemistry. They may be part of a system controlling a manufacturing process, activating a warning system, controlling vehicle motion or monitoring  patient vital signs, to name just a few.

Sensor devices come in various forms and utilize different laws of physics. Fluctuations in sensible heat expand or contract a liquid column and form a thermometer when viewed against a calibrated reference scale. Differential thermal expansion of a bi-metallic strip provides mechanical motion to operate a switch or move a needle on a calibrated gauge. Volume or pressure changes resulting from thermal expansion  (or contraction) of liquid in a sensing well create bellows or diaphragm movement useful for operating a switch or providing control of process gradients. Streetlights go on when the daylight dims the photocell output. Forces can be measured by detecting mechanical displacement, balance changes, elastic material movement or variations in electrical  resistance. A sensor that supplies a signal by converting  pressure to electrical voltage or digital output is called a transducer.

Download the complete article here.