SEE "ADC"

THE SUM OF BOTH ATMOSPHERIC PRESSURE AND GAUGE PRESSURE(PSIG); EXAMPLE: IF A PNEUMATIC GAUGE INDICATES 8 PSIG, THE ABSOLUTE PRESSURE WILL 22.7 PSIA (8+14.7).

ABSOLUTE ZERO IS ALSO DEFINED AS "0-KELVIN", WHICH IS THE TEMPERATURE AT WHICH THERMAL ENERGY IS AT ITS MINIMUM.

STANDS FOR "ALTERNATING CURRENT" WHICH IS THE MOST COMMON TYPE USED BECAUSE IT CONSTANTLY REVERSES ITS DIRECTION AT RECURRING INTERVALS.

STANDS FOR AIR CONDITIONING CONTRACTORS OF AMERICA

THE PERCENTAGE (%) OF DEVIATION BETWEEN THE ACTUAL POSITION AND THE THEORETICAL POSITION OF EACH BIT EDGE.

THE DIRECTION OF MAGNITUDE CHANGE OF THE OUTPUT OF A CONTROLLER WITH RESPECT TO THE CHANGE IN THE VARIABLE BEING SENSED; EXAMPLE: DIRECT ACTING.....VARIABLE INCREASES/OUTPUT INCREASES;REVERSE ACTING.....VARIABLE INCREASES/OUTPUT DECREASES.

SEE "SETPOINT, ACTUAL"

A CONTROL DEVICE WHICH IS USED TO REGULATE THE FLOW OF AIR OF DAMPERS; AND/OR USED TO REGULATE THE FLOW OF STEAM, AIR, WATER, AND OTHER TYPES OF MEDIUMS THROUGH VALVES. ACTUATORS ARE ALSO OFTEN REFERRED TO AS MOTORS OR OPERATORS.

WHEN AUTOMATIC MEANS ARE USED TO CHANGE THE TYPE OR INFLUENCE OF CONTROL PARAMETERS IN SUCH A WAY AS TO IMPROVE THE PERFORMANCE OF THE CONTROL SYSTEM

STANDS FOR "ANALOG-TO-DIGITAL CONVERTER:.

STANDS FOR AMERICAN GAS ASSOCIATION

REFER TO "AIR HANDLING UNIT"

A MECHANICAL SYSTEM CONSISTING OF A SUPPLY-AIR FAN(s), HEATING OR COOLING COILS, FILTERS, AND OUTDOOR AIR & RETURN DAMPERS. IT MAY DELIVER AIR TO A SINGLE SPACE, TO MULTIPLE ZONES, OR TO MULTIPLE CONSTANT-VOLUME OR VARIABLE-VOLUME AIR TERMINAL UNITS.

AN ALARM SCENARIO WHERE A BAND IS CREATED AROUND THE CONTROL SETPOINT

SIMILAR TO ALARM BAND EXCEPT IT ONLY CREATES A BAND ON ONE SIDE OF THE ALARM SETPOINT

AN ALARM THAT SIGNALS WHEN THE PROCESS VARIABLE GOES ABOVE THE ALARM SETPOINT

AN ALARM THAT SIGNALS WHEN THE PROCESS VARIABLE GOES BELOW THE ALARM SETPOINT

AN ALARM THAT IS SET-UP TO OCCUR WHEN THE TEMPERATURE CONTROLLER IS PLACED INTO A MANUAL MODE OF OPERATION

A TYPE OF ALARM THAT DETERMINES AN ALARM CONDITION ON POWER-UP OF THE CONTROLLER

AN ALARM THAT WILL SIGNAL WHEN THERE IS AN EXCESSIVE CHANGE IN THE PROCESS VARIABLE VALUE (PV)

SEE "CONTROL ALGORITHM"

SEE "AC"

STANDS FOR "ARITHMETIC LOGIC UNIT".

AN ALLOY WHICH IS MADE UP OF ALUMINUM-NICKEL AND IS USED IN TYPE "K" THERMOCOUPLES.

ALSO REFERRED TO AS "AMBIENT TEMPERATURE" WHICH IS THE TEMPERATURE OF THE SURROUNDING AIR THAT COMES IN CONTACT WITH THERMOSTATS, HUMIDISTATS, ECT.

SEE "AMBIENT"

SEE "AMBIENT"

SEE "AWG"

AN INDICATOR/METER  WHICH IS USED TO MEASURE CURRENT.

SEE "AMPERE"

ALSO REFERRED TO AS AN "AMP", WHICH IS USED TO DEFINE THE FLOW OF ELECTRICAL CURRENT IN A CIRCUIT

A PROPORTIONAL TYPE OF SIGNAL WHOSE LEVEL VARIES CONTINUOUSLY AND SMOOTHLY IN FREQUENCY OR AMPLITUDE.

A CIRCUIT WHOSE OUTPUT IS AN EXACT REPRODUCTION OF ITS INPUT.

MEASURES THE SPEED OR FORCE OF AN AIR STREAM

STANDS FOR "AMERICAN NATIONAL STANDARDS INSTITUTE"

STANDS FOR THE AIR CONDITIONING & REFRIGERATION INSTITUTE

THE AMERICAN STANDARD CODE WHICH USES EITHER A SEVEN OR EIGHT BIT CODE WHICH IS USED TO REPRESENT ALPHA-NUMERIC CHARACTERS.

STANDS FOR " AMERICAN SOCIETY OF MECHANICAL ENGINEERS"

STANDS FOR "AMERICAN SOCIETY FOR TESTING AND MATERIALS"

STANDS FOR "AUTOMATIC TEMPERATURE COMPENSATION"

THE FUNCTION OF SOME PROCESS TEMPERATURE CONTROLLERS THAT CONTINUOUSLY MONITORS THE PROCESS AND NATURAL DISTURBANCES AND MAKES ADJUSTMENTS IN THE TUNING PARAMETERS TO COMPENSATE OR IMPROVE PERFORMANCE

A CONTROL MODULE THAT IS USUALLY PLACED BETWEEN THE ACTUATOR & CONTROLLER THAT MODIFIES THE CONTROLLER SIGNAL IN SOME MANNER BEFORE THE SIGNAL REACHES THE ACTUATOR; FOR EXAMPLE: RELAYS & SWITCHES.

A SENSING DEVICE THAT EXTENDS ACROSS THE WHOLE DUCT AND SENSES THE AVERAGE TEMPERATURE.

STANDS FOR "AMERICAN WIRE GAGE", AND IS MOST COMMONLY USED WHEN  SPECIFYING THE GAGE OF A THERMOCOUPLE.

A MULTIPLE,IMPELLER- BLADE FAN THAT MOVES AIR ALONG THE LENGTH OF ITS AXLE. AXIAL FANS ARE USUALLY FLANGED, HEAVY-GAUGED CYLINDRICAL ENCLOSURES WHICH MOUNT DIRECTLY INTO ROUND DUCTWORK.