Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.1
35. COMBINED GLOSSARY OF TERMS
35.1 A
abort - the disrupption of normal operation.
absolute pressure - a pressure measured relative to zero pressure.
absorption loss - when sound or vibration energy is lost in a transmitting or reflecting medium. This is the
result of generation of other forms of energy such as heat.
absorbtive law - a special case of Boolean algebra where A(A+B) becomes A.
AC (Alternating Current) - most commonly an electrical current and voltage that changes in a sinusoidal
pattern as a function of time. It is also used for voltages and currents that are not steady (DC).
Electrical power is normally distributed at 60Hz or 50Hz.
AC contactor - a contactor designed for AC power.
acceptance test - a test for evaluating a newly purchased system’s performance, capabilities, and conformity
to specifications, before accepting, and paying the supplier.
accumulator - a temporary data register in a computer CPU.
accuracy - the difference between an ideal value and a physically realizable value. The companion to
accuracy is repeatability.
acidity - a solution that has an excessive number of hydrogen atoms. Acids are normally corrosive.
acoustic - another term for sound.
acknowledgement (ACK) - a response that indicates that data has been transmitted correctly.
actuator - a device that when activated will result in a mechanical motion. For example a motor, a solenoid
valve, etc.
A/D - Analog to digital converter (see ADC).
ADC (Analog to Digital Converter) - a circuit that will convert an analog voltage to a digital value, also
refered to as A/D.
ADCCP (Advanced Data Communications Procedure) - ANSI standard for synchronous communication
links with primary and secondary functions.
address - a code (often a number) that specifies a location in a computers memory.
address register - a pointer to memory locations.
adsorption - the ability of a material or apparatus to adsorb energy.
agitator - causes fluids or gases to mix.
AI (Artificial Intelligence) - the use of computer software to mimic some of the cognitive human processes.
air dump valve - this valve will open to release system pressure when system power is removed.
algorithms - a software procedure to solve a particular problem.
aliasing - in digital systems there are natural limits to resolution and time that can be exceeded, thus aliasing
the data. For example. an event may happen too fast to be noticed, or a point may be too small to
be displayed on a monitor.
alkaline - a solution that has an excess of HO pairs will be a base. This is the compliment to an acid.
alpha rays - ions that are emitted as the result of atomic fission or fusion.
alphanumeric - a sequence of characters that contains both numbers and letters.
ALU (Arithmetic Logic Unit) - a part of a computer that is dedicated to mathematical operations.
AM (Amplitude Modulation) - a fixed frequency carrier signal that is changed in amplitude to encode a
change in a signal.
ambient - normal or current environmental conditions.
ambient noise - a sort of background noise that is difficult to isolate, and tends to be present throughout the
volume of interest.
ambient temperature - the normal temperature of the design environment.
amplifier - increased (or possibly decreases) the magnitude or power of a signal.
analog signal - a signal that has continuous values, typically voltage.
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