Glossary of Terms
- ac
- type of electrical current, the direction of which is reversed at regular intervals or cycles
- ac line frequency
- the frequency of the alternating current power line measured in Hertz (Hz), usually 50 or 60Hz.
- accuracy
- the extent to which results of a calculation or the readings of an instrument approach the true values of the calculated or measured quantities
- active components
- electronics components, such as transistors, diodes, electron tubes, thyristors, etc which can operate on an applied electrical signal as to change its basic characteristics ie: rectification, amplification, switching, etc.
- actual
- the present value of the controlled variable
- alarm
- a signal indicating that a process has exceeded or fallen below the set or limit point
- alarm delay
- the lag time before an alarm is activated
- alarm module
- a controller software and hardware combination configured to alert an operator or perform another function in response to a problem in the thermal system
- alarm silence
- feature for disabling an alarm relay output
- alpha
- temperature coefficient of the change in electrical resistance of a material, indicating the basic change in electrical resistance in a material for each ºC in temperature
- alternating current
- type of electrical current, the direction of which is reversed at regular intervals or cycles
- American Wire Gauge
- (AWG) a standard system for specifying wire diameter. Also referred to as the Brown and Sharpe (B&S) wire gauge
- ammeter
- an instrument that measures the magnitude of an electrical current in amperes
- ampere
- the unit of measurement of the rate of flow of electric current; one coulomb (6.25 x 10^18 electrons) per second
- analog
- a method of representing data using the amplitude of a signal
- analog output
- a voltage or current signal that is a continuous function of the measured parameter
- ANSI
- American National Standards Institute; a voluntary organization of manufacturing industries that publishes standards for a variety of products
- ASME
- American Society of Mechanical Engineers
- ASTM
- American Society for Testing Materials
- atmosphere
- the ambient environment
- atmospheric pressure
- pressure, in pounds per square inch or grams per square centimeter, exerted by the earth's atmosphere upon bodies located within it
- auto-tune
- a feature that automatically sets temperature control PID values to match a particular thermal system
- automatic mode
- a feature that allows the controller to set PID control outputs in response to the set point and the process variable (PV)
- automatic reset
- upon a certain preset condition the system is restored to the original setting
- auxiliary output
- an output that controls external activities that are not directly related to the primary control output
- AWG
- American Wire Gauge, a standard system for specifying wire diameter. Also referred to as the Brown and Sharpe (B&S) wire gauge
