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.

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.

Positive displacement Flowmeter - Variety of transducers used to measure flow. Typical output is pulse train.

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.

23.4 SENSOR GLOSSARY