23.4 SENSOR GLOSSARY
Ammeter - A meter to indicate electrical current. It is normally part of a DMM
Bellows - This is a flexible volumed that will expand or contract with a pressure change. This often looks like a cylinder with a large radius (typ. 2") but it is very thin (type 1/4"). It can be set up so that when pressure changes, the displacement of one side can be measured to determine pressure.
Bourdon tube - Widely used industrial gage to measure pressure and vacuum. It resembles a crescent moon. When the pressure inside changes the moon shape will tend to straighten out. By measuring the displacement of the tip the pressure can be measured.
Chromatographic instruments - laboratory-type instruments used to analyze chemical compounds and gases.
Inductance-coil pulse generator - transducer used to measure rotational speed. Output is pulse train.
Interferometers - These use the interference of light waves 180 degrees out of phase to determine distances. Typical sources of the monochromatic light required are lasers.
Linear-Variable-Differential transformer (LVDT) electromechanical transducer used to measure angular or linear displacement. Output is Voltage
Manometer - liquid column gage used widely in industry to measure pressure.
Ohmmeter - meter to indicate electrical resistance
Optical Pyrometer - device to measure temperature of an object at high temperatures by sensing the brightness of an objects surface.
Orifice Plate - widely used flowmeter to indicate fluid flow rates
Photometric Transducers - a class of transducers used to sense light, including phototubes, photodiodes, phototransistors, and photoconductors.
Piezoelectric Accelerometer - Transducer used to measure vibration. Output is emf.
Pitot Tube - Laboratory device used to measure flow.
Positive displacement Flowmeter - Variety of transducers used to measure flow. Typical output is pulse train.
Potentiometer - instrument used to measure voltage
Pressure Transducers - A class of transducers used to measure pressure. Typical output is voltage. Operation of the transducer can be based on strain gages or other devices.
Radiation pyrometer - device to measure temperature by sensing the thermal radiation emitted from the object.
Resolver - this device is similar to an incremental encoder, except that it uses coils to generate magnetic fields. This is like a rotary transformer.
Strain Gage - Widely used to indicate torque, force, pressure, and other variables. Output is change in resistance due to strain, which can be converted into voltage.
Thermistor - Also called a resistance thermometer; an instrument used to measure temperature. Operation is based on change in resistance as a function of temperature.
Thermocouple - widely used temperature transducer based on the Seebeck effect, in which a junction of two dissimilar metals emits emf related to temperature.
Turbine Flowmeter - transducer to measure flow rate. Output is pulse train.
Venturi Tube - device used to measure flow rates.
