Fundamentals of Industrial Instrumentation and Process Control
By William C. Dunn

Glossary

A-B

Absolute accuracy
The accuracy stated as a definite amount, i.e., not as a percentage.
Absolute position measurement
Position measured from a fixed point.
Absolute pressure
Pressure measured with reference to a perfect vacuum.
Accelerometer
A sensor for measuring acceleration or the rate of change of velocity.
Accuracy
A measure of the difference between the indicated value and the true value.
Actuator
A device that performs an action on one of the input variables of a process according to a signal received from the controller.
ADC
An analog-to-digital converter that converts an analog voltage or current into a digital signal.
Alarm
A warning that a variable has exceeded set limits.
Alternating current
Current that flows in one direction during one half of a regular time period and the opposite direction during the other half.
Ammeter
An instrument for measuring electrical current or electron flow.
Ampere
The unit of current or electron flow.
Amplifier
An electrical circuit that increases the magnitude of a signal.
Analog
A continuously varying signal.
Aneroid barometer
A barometer which uses an evacuated capsule as a sensing element.
Anticipatory action

See Derivative action.

Aqueous solution
A solution containing water.
Atmospheric pressure
The pressure acting on objects on the earth's surface caused by the weight of the air in the earth's atmosphere, normally measured at sea level.
Barometer
An instrument used for measuring atmospheric pressure.
Bellows
A pressure sensor that converts pressure into linear displacement.
Bernoulli equation
A flow equation based on the conservation of energy which...
Copyright The McGraw-Hill Companies, Inc. 2005 under license agreement with Books24x7
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