Industry Terms Glossary

A/D SEE 'ADC'
ABSOLUTE PRESSURE 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 ABSOLUTE ZERO IS ALSO DEFINED AS '0-KELVIN', WHICH IS THE TEMPERATURE AT WHICH THERMAL ENERGY IS AT ITS MINIMUM.
AC STANDS FOR 'ALTERNATING CURRENT' WHICH IS THE MOST COMMON TYPE USED BECAUSE IT CONSTANTLY REVERSES ITS DIRECTION AT RECURRING INTERVALS.
ACCA STANDS FOR AIR CONDITIONING CONTRACTORS OF AMERICA
ACCURACY THE PERCENTAGE (%) OF DEVIATION BETWEEN THE ACTUAL POSITION AND THE THEORETICAL POSITION OF EACH BIT EDGE.
ACTION 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.
ACTUAL SETPOINT SEE 'SETPOINT, ACTUAL'
ACTUATOR 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.
ADAPTIVE CONTROL 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
ADC STANDS FOR 'ANALOG-TO-DIGITAL CONVERTER:.
AGA STANDS FOR AMERICAN GAS ASSOCIATION
AHU REFER TO 'AIR HANDLING UNIT'
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.
ALARM BAND AN ALARM SCENARIO WHERE A BAND IS CREATED AROUND THE CONTROL SETPOINT
ALARM DEVIATION SIMILAR TO ALARM BAND EXCEPT IT ONLY CREATES A BAND ON ONE SIDE OF THE ALARM SETPOINT
ALARM, HIGH PROCESS VARIABLE AN ALARM THAT SIGNALS WHEN THE PROCESS VARIABLE GOES ABOVE THE ALARM SETPOINT
ALARM, LOW PROCESS VARIABLE AN ALARM THAT SIGNALS WHEN THE PROCESS VARIABLE GOES BELOW THE ALARM SETPOINT
ALARM, MANUAL AN ALARM THAT IS SET-UP TO OCCUR WHEN THE TEMPERATURE CONTROLLER IS PLACED INTO A MANUAL MODE OF OPERATION
ALARM, POWER-UP A TYPE OF ALARM THAT DETERMINES AN ALARM CONDITION ON POWER-UP OF THE CONTROLLER
ALARM, RATE-OF-CHANGE AN ALARM THAT WILL SIGNAL WHEN THERE IS AN EXCESSIVE CHANGE IN THE PROCESS VARIABLE VALUE (PV)
ALGORITHM SEE 'CONTROL ALGORITHM'
ALTERNATING CURRENT SEE 'AC'
ALU STANDS FOR 'ARITHMETIC LOGIC UNIT'.
ALUMEL AN ALLOY WHICH IS MADE UP OF ALUMINUM-NICKEL AND IS USED IN TYPE 'K' THERMOCOUPLES.
AMBIENT ALSO REFERRED TO AS 'AMBIENT TEMPERATURE' WHICH IS THE TEMPERATURE OF THE SURROUNDING AIR THAT COMES IN CONTACT WITH THERMOSTATS, HUMIDISTATS, ECT.
AMBIENT CONDITIONS SEE 'AMBIENT'
AMBIENT TEMPERATURE SEE 'AMBIENT'
AMERICAN WIRE GAGE SEE 'AWG'
AMMETER AN INDICATOR/METER  WHICH IS USED TO MEASURE CURRENT.
AMP SEE 'AMPERE'
AMPERE ALSO REFERRED TO AS AN 'AMP', WHICH IS USED TO DEFINE THE FLOW OF ELECTRICAL CURRENT IN A CIRCUIT
ANALOG A PROPORTIONAL TYPE OF SIGNAL WHOSE LEVEL VARIES CONTINUOUSLY AND SMOOTHLY IN FREQUENCY OR AMPLITUDE.
ANALOG OUTPUT A CIRCUIT WHOSE OUTPUT IS AN EXACT REPRODUCTION OF ITS INPUT.
ANEMOMETER MEASURES THE SPEED OR FORCE OF AN AIR STREAM
ANSI STANDS FOR 'AMERICAN NATIONAL STANDARDS INSTITUTE'
ARI STANDS FOR THE AIR CONDITIONING & REFRIGERATION INSTITUTE
ASCII THE AMERICAN STANDARD CODE WHICH USES EITHER A SEVEN OR EIGHT BIT CODE WHICH IS USED TO REPRESENT ALPHA-NUMERIC CHARACTERS.
ASME STANDS FOR ' AMERICAN SOCIETY OF MECHANICAL ENGINEERS'
ASTM STANDS FOR 'AMERICAN SOCIETY FOR TESTING AND MATERIALS'
ATC STANDS FOR 'AUTOMATIC TEMPERATURE COMPENSATION'
AUTO TUNE 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
AUXILIARY DEVICE 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.
AVERAGING ELEMENT A SENSING DEVICE THAT EXTENDS ACROSS THE WHOLE DUCT AND SENSES THE AVERAGE TEMPERATURE.
AWG STANDS FOR 'AMERICAN WIRE GAGE', AND IS MOST COMMONLY USED WHEN  SPECIFYING THE GAGE OF A THERMOCOUPLE.
AXIAL FAN 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.

B & S GAUGE THE SAME AS AWG, AMERICAN WIRE GAUGE.
BAKELITE SEE 'PHENOLIC'
BANDWIDTH AN 'AREA' AROUND THE SETPOINT OF A CONTROLLER AT WHICH PROPORTIONAL CONTROL OCCURS.
BAUD RATE STANDARD TRANSMISSION RATES FOR SENDING OR RECEIVING DATA, AND THE DATA TRANSMISSION SPEED IS EQUAL TO THE NUMBER OF BITS PER SECOND, FOR EXAMPLE: 400 BAUD = 400 BITS PER SECOND
BCD SEE 'BINARY CODED DECIMAL'
BHP BRAKE HORSEPOWER
BIMETAL TWO METALS THAT WHEN EITHER HEATED OR COOLED WARP AND CAN CAUSE OTHER DEVICES OR VALVES TO OPEN OR CLOSE
BINARY CODED DECIMAL ALSO REFERRED TO IN-SHORT AS 'BCD', WHICH IS A NOTATION IN WHICH THE INDIVIDUAL DECIMAL DIGITS ARE REPRESENTED BY A GROUP OF BINARY BITS. FOR EXAMPLE: 8-4-2-1 CODED DECIMAL NOTATION EACH DECIMAL DIGIT IS REPRESENTED BY FOUR BINARY BITS
BIOS STANDS FOR 'BASIC INPUT/OUTPUT SIGNAL'
BIPOLARITY OCCURS WHEN A METER DISPLAYS BOTH POSITIVE AND NEGATIVE READINGS
BIT STANDS FOR 'BINARY DIGIT', ALMOST ALWAYS ASSOCIATED WITH COMPUTERS OR COMPUTER-BASED PROGRAMS. EXAMPLE: 8 BITS = 1 BYTE.
BOILER A CLOSED VESSEL WHERE GAS OR OIL IS BURNED IN ORDER TO GENERATE STEAM OR HOT WATER.
BPS STANDS FOR 'BITS PER SECOND'
BRAKE HORSEPOWER THE TOTAL HORSEPOWER APPLIED TO THE DRIVE SHAFT OF ANY PIECE OF ROTATING EQUIPMENT; THE ACTUAL POWER REQUIRED TO DRIVE A FAN OR A PUMP.
BRANCH LINES THE TUBING IN A PNEUMATIC CONTROL SYSTEM WHICH CARRIES THE OUTPUT SIGNAL FROM THE CONTROLLER TO THE AUXILIARY DEVICES OR ACTUATORS/OPERATORS.
BRIDGE A CONTROL DEVICE THAT RECEIVES THE RESISTANCE CHANGE FROM THE SENSOR AND PRODUCES A LOW-VOLTAGE CHANGE THAT IS AMPLIFIED TO A HIGHER LEVEL WHICH BECOMES THE CONTROLLER OUTPUT. THE 'BRIDGE' IS USUALLY PART OF THE CONTROLLER, OR CAN BE A SEPARATE MODULE.
BTU STANDS FOR 'BRITISH THERMAL UNIT', WHICH IS THE ENERGY OR HEAT THAT IS REQUIRED TO RAISE THE TEMPERATURE OF ONE POUND OF WATER 1 DEGREE (F) UNDER STANDARD PRESSURE.
BUMP A SUDDEN INCREASE IN THE OUTPUT POWER INITIATED BY A TEMPERATURE CONTROLLER IN ORDER TO DETERMINE THE SYSTEM RESPONSE DURING A SELF-TUNING PROCEDURE
BUTTERFLY VALVE A VALVE WHICH NORMALLY SERVES AS A FLUID-FLOW REGULATING DEVICE. ALSO, NORMALLY HAS AN INTERNAL ROTATABLE DISC.
BYPASS CONTROL DAMPER A DAMPER WHICH IS MOUNTED INSIDE OF A DUCT THAT PROVIDES AN ALTERNATE PATH FOR AIR TO FLOW.

C/D SEE 'CONTROLLED DEVICE'
CALIBRATION ADJUSTING, VERIFYING, OR TUNING A DEVICE IN AN EFFORT TO REINSTATE THE DEVICES ACCURACY AND STABILITY
CALIBRATION POINT THE OUTPUT VOLTAGE OF A CONTROLLER WHEN THE SETPOINT AND CONTROL POINTS ARE EQUAL.
CANADIAN STANDARDS ASSOC. SEE 'CSA'
CAPP/USA YOUR NATIONAL SUPPLIER FOR ALL NAME BRANDS OF PROCESS INSTRUMENTATION, COMBUSTION FLAME-SAFEGUARD, AND HEATING, VENTILATING, & AIR CONDITIONING (HVAC) PARTS, CONTROLS, AND DEVICES-(800) 356-8000
CASCADE CONTROL WHEN THE OUTPUT OF ONE DEVICE IS THE SETPOINT FOR ANOTHER DEVICE
CAVITATION OCCURS IN FLOWING LIQUID WHEN THE PRESSURE FALLS BELOW THE VAPOR PRESSURE OF THE LIQUID CAUSING THE LIQUID TO VAPORIZE AND BUBBLE. THE BUBBLES ARE CARRIED THROUGH THE PUMP OR VALVE INLET TO A ZONE OF HIGHER PRESSURE WHERE THEY COLLAPSE WITH GREAT FORCE.
CCW STANDS FOR COUNTER CLOCKWISE
CELSIUS STANDS FOR 'CENTIGRADE' AND IS MEASURED BY 0 DEGREES AT THE ICIER POINT AND 100 DEGREES AT THE BOILING POINT OF WATER.
CFM STANDS FOR 'CUBIC FEET PER MINUTE', THE RATE OF AIR-VOLUME DELIVERY WHICH IS A STANDARD MEASURE FOR HVAC DUCTED SYSTEMS.
CLOSE-OFF THE MAXIMUM AMOUNT OF PRESSURE DROP THAT A VALVE CAN BE SUBJECTED TO WHEN IT'S FULLY CLOSED.
CLOSED LOOP A CONTROL SYSTEM THAT HAS A SENDING DEVICE FOR PROCESS VARIABLE FEEDBACK
CMR STANDS FOR 'COMMON MODE REJECTION'.
CMV STANDS FOR 'COMMON MODE VOLTAGE'
COLD DECK THE PART OF THE DUCT THAT CONTAINS THE CHILLED WATER COIL OR THE DX COIL.
COLD JUNCTION THE POINT OF CONNECTION BETWEEN THE THERMOCOUPLE'S METALS AND AN ELECTRONIC DEVICE/INSTRUMENT
COLD JUNCTION COMPENSATION AN ELECTRONIC MEANS USED TO COMPENSATE FOR THE EFFECT OF TEMPERATURE AT THE COLD JUNCTION
COMFORTABILITY ZONE ALSO REFERRED TO AS THE 'COMFORT ZONE', WHICH IS THE RANGE OF TEMPERATURES & HUMIDITIES WHICH MAKE THE MAJORITY OF PEOPLE FEEL COMFORTABLE. THIS IS USUALLY BETWEEN 67F AND 79F, AND 20% TO 60% RELATIVE HUMIDITY.
COMMON MODE SEE 'CONTROL MODE'
CONDUCTION HEAT ENERGY WHICH IS TRANSMITTED BY DIRECT CONTACT.
CONDUCTOR WIRE WIRE THAT IS DESIGNED TO CARRY ELECTRICAL CURRENT BUT IS NOT INSULATED
CONFIGURATION CAN ALSO BE REFERRED TO AS SET-UP, WHICH IS THE SELECTION OF HARDWARE DEVICES AND SOFTWARE ROUTINES THAT FUNCTION TOGETHER
CONSTANT VOLUME CONTROL A SYSTEM THAT CHANGES THE SUPPLY AIR TEMPERATURE IN RESPONSE TO SPACE LOAD, WHILE MAINTAINING CONSTANT AIR FLOW.
CONSTANTAN THE ALLOY WHICH IS MADE-UP OF COPPER & NICKEL AND IS PRIMARILY USED IN TYPE J, E, & T THERMOCOUPLES
CONTROL ACTION THE SLOPE OF THE OUTPUT OF AN INSTRUMENT OR DEVICE IN REFERENCE TO THE INPUT. FOR EXAMPLE: DIRECT OUTPUT INCREASES ON RISE OF INPUT. TYPICAL COOLING RESPONSE OR REVERSE OUTPUT DECREASES ON RISE OF INPUT(TYPICAL HEATING RESPONSE)
CONTROL ACTION, ADAPTIVE SEE 'ADAPTIVE CONTROL'
CONTROL ACTION, DERIVATIVE (RATE) PART OF THE CONTROLS ALGORITHM THAT REACTS TO THE RATE OF CHANGE OF THE PROCESS VARIABLE
CONTROL ACTION, INTEGRAL (RESET) PART OF THE CONTROLS ALGORITHM THAT REACTS TO OFFSET BETWEEN SETPOINT & PROCESS VARIABLE
CONTROL ACTION, PID PID IS THE CONTROL ACTION OF PROPORTIONAL + INTEGRAL + DERIVATIVE WHICH IS THE CONTROL ALGORITHM THAT PROVIDES PROPORTIONAL CONTROL WITH BOTH INTEGRAL & DERIVATIVE ACTIONS
CONTROL ACTION, PROPORTIONAL (P) WHEN THERE IS A CONTINUOUS LINEAR RELATION BETWEEN THE OUTPUT AND THE INPUT
CONTROL ACTION, PROPORTIONAL + DERIVATIVE A CONTROL ALGORITHM THAT PROVIDES PROPORTIONAL CONTROL WITH THE ADDITION OF DERIVATIVE ACTION IN ORDER TO COMPENSATE FOR OFFSETS BETWEEN SETPOINT & PROCESS VARIABLE
CONTROL ACTION, PROPORTIONAL + INTEGRAL A CONTROL ALGORITHM THAT PROVIDES PROPORTIONAL CONTROL WITH THE ADDITION OF INTEGRAL ACTION IN ORDER TO COMPENSATE FOR OFFSETS BETWEEN SETPOINT & PROCESS VARIABLE
CONTROL ALGORITHM A MATHMATICAL REPRESENTATION OF THE CONTROL ACTION TO BE PERFORMED
CONTROL MODE THE CONTROL MODE, OUTPUT, OR ACTION USED BY A PROCESS TEMPERATURE CONTROLLER SUCH AS PID, ON/OFF, TIME-PROPORTIONING, ECT.
CONTROL MODE, AUTOMATIC A METHOD OF OPERATION WHICH THE USER SELECTS, WHERE THE CONTROLLER DETERMINES THE CONTROL OUTPUT
CONTROL MODE, MANUAL A METHOD OF OPERATION WHICH THE USER SELECTS, WHERE THE OPERATOR DETERMINES THE CONTROLLER OUTPUT
CONTROL OUTPUT THE END PRODUCT WHICH IS AT SOME DESIRED VALUE THAT IS THE RESULT OF HAVING BEEN PROCESSED OR MANIPULATED
CONTROL POINT THE VALUE OF THE CONTROLLED VARIABLE IN WHICH A CONTROLLER OPERATES TO MAINTAIN.
CONTROL POINT THE TEMPERATURE WHICH A SYSTEM IS MAINTAINED AT
CONTROL, CASCADE SEE 'CASCADE CONTROL'
CONTROL, ON/OFF THE CONTROL OF TEMPERATURE ABOUT A SETPOINT BY TURNING THE OUTPUT FUUL ON BELOW SETPOINT AND FULL OFF ABOVE SETPOINT IN THE HEAT MODE
CONTROLLED DEVICE A DEVICE/UNIT THAT RECEIVES A SIGNAL FROM A CONTROLLER AND POSITIONS THE DAMPER OR VALVE TO MATCH THE CAPACITY TO THE LOAD; EXAMPLE OF THIS IS A MOTORIZED VALVE OR MOTORIZES DAMPER.
CONTROLLED VARIABLE A PROCESS VARIABLE THAT IS TO BE CONTROLLED AT SOME DESIRED VALUE BY MEANS OF MANIPULATING ANOTHER PROCESS VARIABLE
CONTROLLER A CONTROL/DEVICE THAT MONITORS A CONTROLLED VARIABLE AND CHANGES THE POSITION OF SUCH FINAL CONTROL DEVICES AS VALVES, DAMPERS, ECT., AND, MAINTAINS THE VALUE OF THE CONTROLLED VARIABLE AT OR VERY CLOSE TO THE CONTROLLER'S SETPOINT.
CONVECTION HEAT THAT MOVES FROM ONE PLACE TO ANOTHER BY CURRENTS WHICH ARE SET-UP WITHIN EITHER A FLUID MEDIUM, LIQUID, OR VAPOR.
CPS STANDS FOR 'CYCLES PER SECOND', WHICH IN HERTZ (HZ) REPRESENTS THE NUMBER OF PERIODIC EVENTS IN ONE SECOND.
CPS STANDS FOR 'CYCLES PER SECOND', THE NUMBER OF EVENTS IN A ONE (1) SECOND PERIOD OF TIME, USUALLY EXPRESSED IN HERTZ.
CPU CENTRAL PROCESSING UNIT. THE 'BRAINS' OF THE COMPUTER WHICH DIRECTS, EXCECUTES, AND PERFORMS ALL COMMANDS AND PROCESSING FUNCTIONS.
CR STANDS FOR CONDENSATE RETURN
CRYOGENICS TEMPERATURES WHICH ARE EXTREMELY LOW, SUCH AS MINUS 180 DEGREES CELSIUS.
CSA 'CANADIAN STANDARDS ASSOCIATION.'  THE NATIONAL STANDARDS OF CANADA WHICH ARE NORMALLY USED IN THE FIELDS OF SAFETY, BUILDING, CONSTRUCTION, HEALTH, AND THE ENVIRONMENT.
CSA STANDS FOR 'CANADIAN STANDARDS ASSOCIATION', SIMILAR TO THE U.S. EQUIVALANT  U.L. (UNDERWRITERS LABORATORIES)
CT STANDS FOR CURRENT TRANSFORMER
CUBIC FEET PER MINUTE SEE 'CFM.'
CURRENT THE FLOW RATE OF ELECTRICITY
CURRENT PROPORTIONING NORMALLY ASSOCIATED WITH PROCESS TEMPERATURE CONTROLLERS, PROVIDES A CURRENT PROPORTIONAL TO THE AMOUNT OF CONTROL THAT IS REQUIRED
Cv STANDS FOR 'FLOW COEFFICIENT,' WHICH IS THE FLOW OF WATER GALLONS PER MINUTE (GPM) AT A TEMPERATURE OF APPROX. 60F, THAT CAUSES A 1 PSI PRESSURE DROP ACROSS A FULLY-OPENED VALVE.
CW STANDS FOR CLOCKWISE
CYCLE TIME THE TIME THAT IS NECESSARY TO COMPLETE A FULL ON-THRU-OFF PERIOD IN A TIME PROPORTIONING CONTROL SYSTEM

D/A CONVERTER SEE 'DIGITAL-TO-ANALOG CONVERTER'
DAMPING THE DECREASE IN AMPLITUDE OF AN OSCILLATION WHICH IS DUE TO THE DISSIPATION OF ENERGY
DB STANDS FOR DECIBELS
DDC A MICROPROCESSOR-BASED COMPUTER CONTROL SYSTEM THAT PROVIDES DIRECT CONTROL OF THE MANY INDIVIDUAL COMPONENTS OF AN HVAC SYSTEM, WITHOUT THE USE OF CONVENTIONAL DEVICES SUCH AS THERMOSTATS.
DDC NAMES THE TWO PREDOMINANT DDC SYSTEMS IN THE HVAC INDUSTRY TODAY ARE: JOHNSON CONTROLS' 'METASYS' SYSTEM, AND HONEYWELL'S 'DELTA' & 'EXCEL' SYSTEMS.
DEAD TIME THE INTERVAL OF TIME BETWEEN THE INITIATION OF AN INPUT CHANGE OR STIMULUS AND THE START OF THE RESULTING OBSERVABLE RESPONSE
DEADBAND THIS IS AN AREA THAT REPRESENTS 'NO CHANGE'; IN OTHER WORDS, A POINT'S VALUE MUST EITHER GO ABOVE OR BELOW THE DEADBAND IN ORDER TO TRIGGER CONTROL ACTION OR AN ALARM.
DECIBEL SEE 'DB'
DEFAULT SETTINGS PARAMETERS AND/OR SELECTIONS THAT HAVE BEEN MADE AT THE FACTORY
DEGREE INCREMENTAL VALUES ON A TEMPERATURE SCALE. EXAMPLE: 0 TO 240 DEGREES F OR C.
DEGREE DAY (BASIC DEFINITION) A UNIT BASED ON TEMP. & TIME WHICH IS USED IN THE ESTIMATING OF FUEL CONSUMPTION AS WELL AS FOR SPECIFYING THE NOMINAL HEATING LOAD OF BUILDINGS IN THE WINTER TIME.
DEGREE DAY (TECHNICAL DEFINITION) FOR ANY ONE DAY, WHEN THE MEAN TEMP. IS LESS THAN 65 DEG. (F) (18 DEG. C), THERE EXIST AS MANY DEGREE DAYS AS THERE ARE FAHRENHEIT OR CELSIUS DEGREES DIFFERENCE IN TEMP. BETWEEN THE MEAN TEMP. FOR THE DAY AND 65 DEG. (F).
DELTA SYSTEM A DIRECT DIGITAL CONTROL (DDC) SYSTEM DEVELOPED BY HONEYWELL THAT PROVIDES COMPLETE HVAC-BUILDING AUTOMATION
DENSITY MASS PER UNIT OF VOLUME, SUCH AS POUNDS/CUBIC FEET
DERIVATIVE ACTION THAT SENSES THE RATE OF CHANGE OF TEMPERATURE, AND ALSO COMPENSATES TO MINIMIZE OVERSHOOT & UNDERSHOOT
DERIVATIVE ACTION SEE 'CONTROL ACTION, DERIVATIVE'
DEVIATION FROM SETPOINT SEE 'SETPOINT, DEVIATION FROM'
DEW POINT THE SATURATION POINT OF A MIXTURE OF  AIR AND WATER VAPOR
DIALAPAK SAME AS THE DIALATROL, BUT IS A SMALLER, MORE COMPACT VERSION
DIALATROL A TEMPERATURE CONTROL MANUFACTURED BY HONEYWELL THAT EITHER INDICATES AND/OR CONTROLS A PROCESS/LOOP, AND ALSO ACCEPTS A THERMOCOUPLE INPUT(S)
DIFFERENTIAL PRESSURE CONTROL WHEN TWO PRESSURE SENSORS TRANSMIT THEIR SIGNALS TO A CONTROLLER, AND THE CONTROLLER THEN PRODUCES AN OUTPUT TO THE CONTROLLED DEVICE THAT VARIES IN ACCORDANCE WITH THE DIFFERENCE OF THE TWO SENSED PRESSURES
DIFFERENTIAL PRESSURE SWITCH A SWITCH WHICH IS ACTIVATED BY AIR PRESSURE, AND IS OFTEN USED IN SUPPLY DUCTS TO DETECT FLOW OF PRESSURE DROPS ACROSS FILTERS
DIGITAL AN ON/OFF OR TWO POSITION SIGNAL USUALLY ASSOCIATED WITH A DIGITAL CONTROLLER
DIGITAL INPUT THE TERM USED TO DESCRIBE THE STAUS OF A DRY CONTACT, ALSO REFERRED TO AS A 'GATE'
DIGITAL-TO-ANALOG CONVERTER A CIRCUIT THAT ACCEPTS DIGITAL INPUT SIGNALS AND CONVERTS THEM TO ANALOG OUTPUT SIGNALS.
DIN MAINLY ASSOCIATED WITH THE SIZE & PANEL CUT-OUT OF A PROCESS  TEMPERATURE CONTROLLER; DIN IS A GERMAN STANDARD AND STANDS FOR: 'DEUTSCHE INDUSTRIAL NORM'. MEASUREMENT EXAMPLES OF DIN ARE 1/8 & 1/4' DIN TO NAME A FEW
DIP SWITCH STANDS FOR 'DUAL IN-LINE PACKAGE SWITCH'.  MULTIPLE SWITCHES ON ONE CIRCUIT BOARD, EACH SWITCH HAVING THE CAPABILITY OF BEING SET TO EITHER ONE OF TWO POSITIONS.
DIRECT ACTING AN INCREASE IN BRANCH LINE PRESSURE IN RESPONSE TO A RISE IN TEMPERATURE
DIRECT DIGITAL CONTROL SYSTEM SEE 'DDC'
DIRECT RESET ON TYPICALLY TWO INPUT APPLICATIONS, WHEN A DECREASE AT THE SECOND OPEN-LOOP SENSOR CAUSES THE CONTROLLER SETPOINT TO DECREASE
DISCHARGE DAMPER A DAMPER OR DAMPERS WHICH ARE DIRECTLY LOCATED IN THE DISCHARGE OF EITHER A FAN OR A DUCT
DISK OPERATING SYSTEM ALSO REFERRED TO AS 'DOS', CONTROLS THE TRANSFERRING OF INFORMATION TO AND FROM A DISK.
DIVERTING VALVE A THREE-WAY VALVE THAT DIRECTS FLOW TO EITHER OUTLET OR CAN PROPORTION THE FLOW BETWEEN THE TWO OUTLETS. MANT THREE-WAY/DIVERTING VALVES ARE USED FOR WATER-MIXING.
DoD STANDS FOR DEPARTMENT OF DEFENSE
DOS SEE 'DISK OPERATING SYSTEM'
DOWNSCALE BURNOUT SEE 'THERMOCOUPLE DOWNSCALE BURNOUT'
DP STANDS FOR DRIP-PROOF
DPDT STANDS FOR DOUBLE-POLE/DOUBLE-THROW
DROOP NORMALLY OCCURS IN TIME-PROPORTIONAL TEMPERATURE CONTROLLERS. IT IS THE DIFFERENCE IN TEMPERATURE BETWEEN SETPOINT AND WHERE THE TEMPERATURE OF THE SYSTEM STABILIZES.
DRY BULB TEMPERATURE THE AIR TEMPERATURE MEASURED BY A THERMOMETER
DRY CONTACT A CONTACT THAT DOES NOT IMPOSE AN ELECTRONIC SIGNAL FROM AN OUTSIDE SOURCE. A DIRECT SHORT OF NORMALLY-OPEN CONTACTS.
DUAL IN-LINE PACKAGE SWITCH SEE 'DIP SWITCH'
DUPLEX TWO-WAY DATA COMMUNICATION IN BOTH DIRECTIONS; PERTAINING TO DUPLEX THERMOCOUPLES HAVING TWO ELEMENTS
DUPLEX USUALLY ASSOCIATED WITH THERMOCOUPLES, MEANS THAT THERE ARE TWO (2) (DUAL) ELEMENTS INSTEAD OF ONE (1).
DUTY CYCLING REDUCES ELECTRICAL CONSUMPTION BY PERIODICALLY TURNING-OFF EQUIPMENT FOR SHORT PERIODS OF TIME DURING NORMAL OPERATING HOURS. DUTY CYCLING IS NORMALLY A FUNCTION OF AN ENERGY MANAGEMENT SYSTEM.

E-P SWITCH SEE 'ELECTRIC-PNEUMATIC SWITCH'
EA STANDS FOR EXHAUST AIR, AND/OR THE UNIT OF MEASURE: 'EACH'
EARTH GROUND A SPECIFIC TERMINAL USED TO ENSURE BY MEANS OF SPECIAL CONNECTION, THE GROUNDING OF PART OF A DEVICE/CONTROL
ECONOMIZER BAND THE RANGE OF TEMPERATURES WITHIN WHICH AN AIR HANDLER IS IN ECONOMIZER MODE.
ECONOMIZER DEADBAND THE RANGE OF TEMPERATURES BETWEEN THE HIGH END END OF AN ECONOMIZER BAND AND THE FIRST STAGE OF MECHANICAL COOLING.
ECONOMIZER MODE A CONTROL MODE IN WHICH RELIEF DAMPERS AND OUTSIDE RETURN AIR DAMPERS ARE CONTROLLED BY AIR TEMPERATURE IN ORDER TO PROVIDE THE MOST ECONOMICAL HEATING AND/OR COOLING
ELECTRIC-PNEUMATIC SWITCH AN AIR FLOW SWITCH, ELECTRICALLY OPERATED WITH NORMALLY-OPENED & NORMALLY-CLOSED INPUTS WHICH LEAD TO A COMMON OUTPUT
ELECTRO MOTIVE FORCE SEE 'EMF'
ELECTRONIC CONTROLS GENERALLY USE LOW VOLTAGES AND CURRENTS SUCH AS 20 VOLTS OR EVEN LESS.
ELECTRONIC DEVICES SEE 'ELECTRONIC CONTROLS'
EMF STANDS FOR ELECTROMOTIVE FORCE, WHICH IS A RISE IN ELECTRICAL ENERGY
EMI STANDS FOR ELECTROMAGNETIC INTERFERENCE
ENCODER AN ELECTRO-MECHANICAL DEVICE THAT TRANSLATES MECHANICAL MOTION OR POSITION INTO ELECTRICAL SIGNALS.
ENERGY MANAGEMENT A TERM DEVELOPED IN THE 1970'S WHICH PROVIDES SEVERAL TECHNIQUES FOR REDUCING ENERGY CONSUMPTION THROUGHOUT A BUILDING(s) WHILE AT THE SAME TIME MAXIMIZING OPERATING EFFICIENCY.
ENGINEERING UNITS TERMS AND ABBREVIATIONS THAT REPRESENT 'MEASURED UNITS'; SOME EXAMPLES INCLUDE: (VAC) VOLTS ALTERNATING CURRENT; (KW) KILOWATTS; (GPM) GALLONS PER MINUTE; (F) FAHRENHEIT; ECT., ECT.
ENTHALPY MEASURE OF  TOTAL HEAT OF AIR (SENSIBLE + LATENT) THAT IS MEASURED ABOVE AN ARBITRARY DATUM. THE SPECIFIC ENTHALPY OF DRY AIR IS ASSIGNED A VALUE OF ZERO  DEG. (F) AND U.S.  ATMOSPHERIC PRESSURE (29.92' OF MERCURY), IS MEASURED IN BTU PER LB. OF DRY AIR
EP SWITCH SEE 'ELECTRIC-PNEUMATIC SWITCH'
EPROM MAINLY FOUND ON OR ASSOCIATED WITH ELECTRONIC CIRCUITRY/CIRCUIT BOARDS, STANDS FOR 'ERASABLE PROGRAMMABLE READ-ONLY MEMORY'
EUTECTIC TEMPERATURE OCCURS WHENEVER A MIXTURE OF ALLOYS OR METALS REACHES ITS LOWEST POSSIBLE MELTING POINT.
EVAPORATIVE COOLING THE ADIABATIC EXCHANGE OF HEAT BETWEEN AIR AND WATER SPRAY OR WETTED SURFACE. THE WET BULB TEMPERATURE OF THE AIR REMAINS CONSTANT, BUT THE DRY BULB IS DECREASED
EXCEL SYSTEM A DIRECT DIGITAL CONTROL (DDC) SYSTEM DEVELOPED BY HONEYWELL THAT PROVIDES COMPLETE HVAC-BUILDING AUTOMATION
EXHAUST DAMPER THIS TYPE OF SPECIFIC DAMPER NORMALLY OPENS AS THE OUTDOOR AIR DAMPER OPENS AND THE RETURN AIR DAMPER CLOSES. EXHAUST DAMPERS ARE USUALLY FOUND ON OR AS PART OF AIR HANDLING UNITS, AND CAN ALSO BE REFERRED TO AS 'RELIEF DAMPERS'

FACTORY MUTUAL SEE 'FM APPROVED'
FAHRENHEIT THE MOST COMMONLY USED TEMPERATURE SCALE WHICH IS MEASURED IN DEGREES AT 32 DEGREES AT ICE POINT AND 212 DEGREES AT THE BOILING POINT OF WATER.
FALL TIME THE TIME INTERVAL BETWEEN THE POINTS AT WHICH THE INSTANTANEOUS VALUE FALLS FROM 90% TO 10% OF THE SPECIFIED UPPER LIMIT.
FEEDBACK THE PROCESS SIGNAL THAT IS USED IN CONTROL AS A MEASURE OF RESPONSE TO CONTROL ACTION; THE PART OF A CLOSED-LOOP SYSTEM WHICH AUTOMATICALLY BRINGS BACK DATA ABOUT THE CONDITION THAT IS UNDER CONTROL
FEET PER MINUTE SEE 'FPM'
FINISH POINT SEE 'PNEUMATIC FINISH POINT'
FLASH POINT THE TEMPERATURE AT WHICH A FLAMMABLE LIQUID CAN GIVE OFF ENOUGH  VAPOR TO IGNITE OR CAUSE EXPLOSION
FLOATING CONTROL WHEN A TWO-POSITION CONTROLLED DEVICE CAN STOP AT ANY POINT IN ITS STROKE AT LOSS OF CONTROL SIGNAL. THE CONTROLLED DEVICE  WILL HOLD THIS POSITION UNTIL THE CONTROLLER SENSES ANOTHER SIGNAL TO REPOSITION THE CONTROLLED DEVICE.
FLOATING CONTROL ACTION SEE 'FLOATING CONTROL'
FLOW COEFFICIENT SEE 'Cv'
FLUTTER VARIATION IN CYCLE WIDTH FROM CYCLE TO ADJACENT CYCLE.
FM APPROVED STANDS FOR 'FACTORY MUTUAL RESEARCH CORP.' WHICH SETS SAFETY STANDARDS
FPM STANDS FOR 'FEET PER MINUTE', WHICH QUANTIFIES THE VELOCITY OF AIR FLOW
FPM STANDS FOR FEET PER MINUTE
FPS STANDS FOR 'FEET PER SECOND'
FREQUENCY-TO-VOLTAGE CONVERTER AN ELECTRONIC DEVICE WHICH DIRECTLY CONVERTS A FREQUENCY INPUT TO A VOLTAGE OUTPUT.
FS STANDS FOR FULL SCALE

GAIN THE RATIO OF THE CHANGE IN OUTPUT TO THE CHANGE IN INPUT THAT CAUSED IT
GALLONS PER MINUTE SEE 'GPM'
GALVONOMETER DETECTS EXTREMELY SMALL ELECTRICAL CURRENTS
GAUSS ELECTROMAGNETIC UNIT OF MAGNETIC INDUCTION
GPH STANDS FOR 'GALLONS PER HOUR'
GPM STANDS FOR 'GALLONS PER MINUTE', WHICH QUANTIFIES WATER FLOW

HEAD A MEASURE OF PRESSURE WHICH IS EXPRESSED IN FEET; TYPICALLY APPLIES TO CENTRIFUGAL PUMPS, AND INDICATES THE COLUMN HEIGHT OF WATER THAT IS BEING LIFTED BY THE PUMP
HEAT PUMP A UNIT THAT EITHER HEATS OR COOLS A BUILDING BY USING HEAT FROM THE CONDENSER SECTION OR BY USING COOLING FROM THE EVAPORATOR SECTION
HEAT SINK USUALLY FOUND ON CIRCUIT BOARDS AND PRINTED WIRE BOARDS (PWB's), A HEAT SINK ACTS TO DISIPATE THE HEAT OF COMPONENTS THAT ARE MOUNTED ON THE SOLID STATE BOARDS.
HEAT/COOL CONTROL THE METHOD OF CONTROL WHEN THE TEMPERATURE OF THE END PRODUCT IS MAINTAINED BY CONTROLLING TWO FINAL ELEMENTS USING TWO OUTPUTS
HERTZ UNITS WHICH EXPRESS FREQUENCY; ABBREVIATION IS 'HZ'
HOT LEG SEE 'MEASURING JUNCTION'
HUMIDISTAT MEASURES HUMIDITY IN % OF RELATIVE HUMIDITY WHILE SENSING AND CONTROLLING THE MOISTURE CONTENT OF THE AIR
HUNTING WHEN A CONTROLLER CAUSES A MOTOR OR ACTUATOR DEVICE TO CONTINUOUSLY TRAVEL FROM ONE END OF ITS STROKE TO THE OTHER
HUNTING THE OSCILLATION OR FLUCTUATION OF THE PROCESS TEMPERATURE BETWEEN SETPOINT & PROCESS VARIABLE
HVAC STANDS FOR 'HEATING, VENTILATING, & AIR CONDITIONING'
HVAC/R STANDS FOR 'HEATING, VENTILATING, AIR CONDITIONING, & REFRIGERATION'
HYDRAULIC ACTUATOR AN ACTUATOR THAT EITHER OPERATES VALVES OR DAMPERS BY PRODUCING A LINEAR MOTION AS A RESULT OF THE FLUID PRESSURE DEVELOPED FROM A CONTINUOUSLY RUNNING MOTOR PUMPING OIL THROUGH A TRANSDUCER
HYDRONICS THE CONTROL & USE OF WATER AS A HEAT TRANSFER MEDIUM IN AIR CONDITIONING SYSTEMS AND BOILERS
HYGROSCOPIC WATER ABSORBING
HYSTERESIS IN ON/OFF CONTROL, THE TEMPERATURE CHANGE THAT IS NECESSARY TO CHANGE THE OUTPUT FROM FULL ON TO FULL OFF

IC STANDS FOR INTEGRATED CIRCUIT
IMMERSION SENSOR A CONTROL WITH AN  EXTENDED ELEMENT (BULB & CAPILLARY) THAT IS USED TO SENSE THE TEMPERATURE OF STEAM, WATER, ECT. IN LIQUID LINES AND TANKS. IMMERSION SENSORS/CONTROLS MOUNT REMOTELY AND ARE ALSO AVAILABLE IN STRAP-ON MOUNTING
IMPEDANCE OPPOSITION TO THE FLOW OF ELECTRICITY, RESISTIVE + REACTIVE
IN. W.C. SEE 'INCHES OF WATER COLUMN'
INCHES OF WATER COLUMN A TERM OF MEASUREMENT THAT IS PRIMARILY USED TO MEASURE & CONTROL LOW DIFFERENTIAL PRESSURES. LOW DIFFERENTIAL PRESSURES INCLUDE THOSE OF DUCT STATIC PRESSURE; SPACE STATIC PRESSURE; AND THE VELOCITY PRESSURE OF FLOWING AIR IN DUCTS.
INFILTRATION AIR LEAKAGE THROUGH THE JOINTS & CRACKS,  AND WINDOWS & DOORS OF A BUILDING OR STRUCTURE DUE TO EITHER THE ADVERSE PRESSURE EFFECTS OF WIND, OR THE DIFFERENCE IN THE INDOOR & OUTDOOR AIR DENSITY
INFRARED EXCEEDS RED LIGHT FROM 750 NANOMETERS TO 1,000 MICRONS AND IS USED TO DETECT TEMPERATURE & FLAME WITHOUT MAKING PHYSICAL CONTACT. MOSTLY USED IN THE DETECTION OF INFRARED IN FLAME IN BOILERS, BURNERS, OVENS, KILNS, & INCINERATORS.
INLET VANE RESTRICTS AIR FLOW INTO CENTRIFUGAL FAN HOUSINGS, AND RESTRICTS REFRIGERANT FLOW ON CENTRIFUGAL CHILLERS
INPUT PROCESS VARIABLE DATA BEING SUPPLIED TO THE DEVICE. FOR EXAMPLE: FOR A PROCESS TEMPERATURE CONTROLLER THE MOST COMMON FORMS OF INPUT ARE THERMOCOUPLE & R.T.D.
INTEGRAL THE CONTROL ACTION THAT AUTOMATICALLY ELIMINATES OFFSET, OR 'DROP', BETWEEN SETPOINT AND ACTUAL PROCESS TEMPERATURE, AND ALSO 'RESET'
INTEGRAL CONTROL A CONTROL ACTION THAT IS SPECIFICALLY DESIGNED TO EITHER REDUCE OR EVEN ELIMINATE OFFSET IN A PROPORTIONAL CONTROL
INTELLIGENT AUTOMATION ALSO REFERRED TO AS 'I/A', IS A PROCESS CONTROL AUTOMATION SYSTEM DEVELOPED BY FOXBORO CO. (SIEBE) THAT PROVIDES COMPUTER-BASED MONITORING, CONTROLLING, & AUTOMATION TO AN INDUSTRIAL PLANTS PROCESS CONTROL LOOP(s)/SYSTEM
INTERPOLATION A MATHMATICAL PROCESS THAT ESTIMATES A MISSING FUNCTIONAL  VALUE BY TAKING A WEIGHTED AVERAGE OF KNOWN FUNCTIONAL VALUES AT NEIGHBORING POINTS. (THIS IS DONE ELECTRONICALLY IN SOME DEVICES).
INTERVAL TIMER A TIMER THAT HAS ITS OUTPUT OCCUR DURING THE TIMING STATE
IPCEA STANDS FOR THE INSULATED POWER CABLE ENGINEERS ASSOCIATION
IR STANDS FOR INFRA-RED
ISA STANDS FOR INSTRUMENT SOCIETY OF AMERICA
ISOLATION THE ELECTRICAL SEPARATION OF THE SENSOR FROM HIGH VOLTAGE CIRCUITRY. ALLOWS FOR APPLICATION OF GROUNDED OR UNGROUNDED SENSING ELEMENT
ISOTHERMAL MEANS CONSTANT TEMPERATURE.
ITS90 MEANS THE INTERNATIONAL TEMPERATURE SCALE OF 1990 WHICH IS THE PRESENT STANDARD DEFINED BY 17 FIXED POINTS WHICH ARE ASSIGNED STANDARD VALUES. ITS90 SUPERSEDES IPTS68.

JUMPER A WIRE THAT IS USED TO EITHER CONNECT OR BYPASS A POERTION OF A CIRCUIT OR PRINTED WIRE BOARD

K SEE 'KELVIN'
KELVIN KELVIN, WHOSE SYMBOL IS K, IS DEFINED AS THE UNIT OF THERMODYNAMIC TEMPERATURE, PHYSICAL QUANTITY, OR ABSOLUTE TEMPERATURE WHOSE MAGNITUDE IS 1/273.15 OF THE THERMODYNAMIC TEMP. OF ICE POINT.
KHZ STANDS FOR 'KILO HERTZ', A MEASURE OF FREQUENCY.
KILOWATT A KILOWATT OR kw IS EQUAL TO 1000 WATTS
KILOWATT HOUR KILOWATT HOUR OR kwh IS EQUAL TO 1000 WATT HOURS
kva STANDS FOR KILOVOLT AMPERES AND IS EQUAL TO 1000 VOLT AMPS

LAG THE PART OF THE WELL THAT IS BELOW THE HEX AND ABOVE THE THREADS. ITS PURPOSE IS TO EXTEND THROUGHOUT THE LAGGING OF THE VESSEL.
LATENT HEAT THE AMOUNT OF HEAT THAT IS NEEDED IN ORDER TO CHANGE AN AMOUNT OF WATER AT 212 DEGREES (F) (100C) FROM LIQUID TO VAPOR AT CONSTANT BAROMETRIC PRESSURE
LCD STANDS FOR LIQUID CRYSTAL DISPLAY
LED STANDS FOR LIGHT EMITTING DIODE
LINEARIZATION THE FUNCTION THAT IS USED TO AUTOMATICALLY LINEARIZE A NON-LINEAR SIGNAL EITHER FROM A THERMOCOUPLE OR R.T.D. THROUGH THE USE OF LOOK-UP TABLES
LINEARIZATION, SQUARE ROOT THE FUNCTION THAT'S USED TO LINEARIZE A NON-LINEAR SIGNAL CORRESPONDING TO THE FLOW BEING MEASURED BY TRANSMITTERS
LOAD THE DEMAND FOR INPUT TO A PROCESS
LOAD LINE OUT A START-UP OUTPUT VALUE WHICH IS TO BRING INITIAL OUTPUT CLOSER TO THE ACTUAL STEADY STATE OUTPUT
LOAD SHEDDING TO TURN OFF ELECTRICAL LOADS IN ORDER TO LIMIT PEAK ELECTRICAL DEMAND
LOOP POWER AN INTERNAL 24-VOLT CURRENT LIMITED POWER SUPPLY USED TO POWER 2 OR 4 WIRE TRANSMITTERS ON THE INPUT OF A CONTROLLER
LOW PASS INPUT FILTER A METHOD USED TO BLOCK FAST ACTING SIGNALS SUCH AS NOISE, WHILE ALLOWING SLOW ACTING SIGNALS (ACTUAL PROCESS VARIABLE) TO PASS
LPG STANDS FOR LIQUIFIED PETROLEUM GAS
LSIC STANDS FOR 'LARGE SCALE INTEGRATED CIRCUIT'
LUX METER MEASURES ILLUMINANCE

M STANDS FOR 'MEGA', OR ONE MILLION
MAGNETIC FEEDBACK TRANSDUCER ANY TRANSDUCER WHICH RELIES ON CHANGES IN ITS MAGNETIC FIELD TO SEND ITS OUTPUT.
MAINS THE TERM 'MAINS' IN A PNEUMATIC HVAC SYSTEM ARE LINES THAT CARRY AIR AT A CONSTANT SUPPLY PRESSURE WHICH IS GENERALLY 15 TO 25 PSIG
MAKE-UP AIR OUTDOOR AIR THAT IS BROUGHT INTO A BUILDING FOR VENTILATION
MAKE-UP WATER WATER WHICH IS SUPPLIED TO REPLENISH THE WATER THAT IS LOST BY EITHER EVAPORATION OR LEAKS
MANOMETER MEASURES PRESSURES OF VAPORS & GASES
MANUAL RESET I A FEATURE ON A DIGITAL TEMPERATURE CONTROLLER THAT ADJUSTS ITS PROPORTIONING BAND IN RELATIONSHIP TO ITS SET POINT IN AN EFFORT TO ELIMINATE ERRORS.
MANUAL RESET II A SWITCH ON A LIMIT CONTROL, RELAY, OR SAFETY DEVICE THAT MANUALLY RESETS AFTER THE LIMIT HAS BEEN EXCEEDED OR BROKEN.
MEAN TEMPERATURE THE MAXIMUM & MINIMUM TEMPERATURE OF A PROCESS EQUALIBRIUM WHICH IS AVERAGED.
MEASURING JUNCTION THE JUNCTION OF A THERMOCOUPLE THAT IS SUBJECT TO THE TEMPERATURE. ALSO REFERRED TO AS THE 'HOT LEG' OF THE THERMOCOUPLE. THERE ARE THREE (3) BASIC TYPES: GROUNDED, UNGROUNDED, AND REMOTE.
MECHANICAL RELAY SEE 'RELAY (MECHANICAL)'
MENU BLOCK GROUPS OF PARAMETERS ARRANGED IN THE SOFTWARE OF A CONTROLLER
METASYS A DIRECT DIGITAL CONTROL (DDC) SYSTEM DEVELOPED BY JOHNSON CONTROLS THAT PROVIDES COMPLETE HVAC-BUILDING AUTOMATION
MICROAMP MEASURED AS 1 MILLIONTH OF AN AMPERE
MICROCONTROLLER A LARGE-SCALE INTEGRATED CIRCUIT THAT HAS ALL THE FUNCTIONS OF A COMPUTER INCLUDING MEMORY AND INPUT/OUTPUT SYSTEMS
MICROFARAD MEASURED AS 1 MILLIONTH OF A FARAD
MICRON MEASURED AS I MILLIONTH OF A METER
MICROVOLT MEASURED AS 1 MILLIONTH OF A VOLT
MILLIAMP MEASURED AS 1 THOUSANDTH OF AN AMP; ABBREVIATION FOR MILLIAMP IS: mA
MILLIVOLT MEASURED AS 1 THOUSANDTH OF A VOLT; ABBREVIATION IS: mV
MIXING BOX A BOX OR ENCLOSURE THAT HAS DAMPERS IN THE HOT & COLD AIR STREAM THAT MIXES THE TWO (HOT & COLD), AND DELIVERS THE MIXED AIR INTO A SPACE AT A SPECIFIED TEMPERATURE
MOP STANDS FOR 'MOTOR OPERATED POTENTIOMETER'
MOV STANDS FOR 'METAL OXIDE VARISTOR', USED TO PREVENT POWER SURGES & POWER SPIKES.
MS-DOS SEE 'DISK OPERATING SYSTEM'
MSDS STANDS FOR MATERIAL SAFETY DATA SHEETS
MTBF STANDS FOR 'MEAN TIME BETWEEN FAILURE', WHICH IS AN INDICATION OF THE AVERAGE LIFE EXPECTANCY OF A UNIT WHEN OPERATED WITHIN ITS DESIGN LIMITATIONS.
MULTIDRIVE AN APPLICATION WHERE MORE THAN ONE MOTOR IS BEING CONTROLLED BY ONE CONTROLLER. THERE ARE THREE (3) TYPES: PARALLEL, PROGRESSIVE, & CASCADED.

N.C. SEE 'NORMALLY CLOSED'
N.O. SEE 'NORMALLY OPEN'
NBS STANDS FOR NATIONAL BUREAU OF STANDARDS
NEC STANDS FOR NATIONAL ELECTRIC CODES
NEMA STANDS FOR NATIONAL ELECTRICAL MANUFACTURERS' ASSOCIATION
NETWORK 8000 A DIRECT DIGITAL CONTROL (DDC) SYSTEM DEVELOPED BY BARBER-COLMAN CO. (SIEBE CO.) THAT PROVIDES COMPLETE HVAC-BUILDING AUTOMATION
NFPA STANDS FOR THE NATIONAL FIRE PROTECTION ASSOCIATION
NIGHT SETBACK A CONDITION GENERALLY ASSOCIATED WITH THERMOSTATS, THAT IS WHEN THE SETPOINT OF THE THERMOSTAT IS SET/SHIFTED TO A LOWER TEMPERATURE DURING UNOCCUPIED HOURS, ESPECIALLY DURING THE HEATING SEASON
NIGHT SETUP GENERALLY ASSOCIATED WITH THERMOSTATS, WHEN THE SETPOINT IS SET/SHIFTED TO A HIGHER TEMPERATURE DURING UNOCCUPIED HOURS, ESPECIALLY DURING THE COOLING SEASON
NIST STANDS FOR NATIONAL INSTITUTE FOR STANDARDS AND TECHNOLOGY.
NOISE AN UNWANTED COMPONENT OF A SIGNAL OR VARIABLE
NORMALLY CLOSED A TERM/CONDITION THAT APPLIES TO A CONTROLLED DEVICE WHICH CLOSES WHEN EITHER A POWER FAILURE OCURRS, OR WHEN CONTROL PRESSURE IS REMOVED
NORMALLY OPEN A TERM/CONDITION THAT APPLIES TO A CONTROLLED DEVICE THAT IS OPEN WHEN ALL OPERATING FORCE IS LOST, SUCH AS IN A POWER FAILURE
NPT STANDS FOR NATIONAL PIPE THREAD

O.D. STANDS FOR OUSIDE DIAMETER
OA STANDS FOR OUTDOOR AIR
OCCUPIED MODE A CONTROL MODE THAT IS USED TO HEAT OR COOL BUILDINGS WHILE THEY ARE OCCUPIED
OFFSET THE AMOUNT OF DIFFERENCE BETWEEN CONTROL POINT AND SETPOINT IN A PROPORTIONAL CONTROL SYSTEM
OFFSET THE ADJUSTMENT TO THE ACTUAL INPUT TENMPERATURE AND TO THE TEMPERATURE VALUES THAT THE CONTROLLER USES FOR DISPLAY & CONTROL
OHMETER USED TO MEASURE ELECTRICAL RESISTANCE
ON/OFF CONTROL SEE 'CONTROL, ON/OFF'
OPEN LOOP A CONTROL SYSTEM WITH NO SENSORY FEEDBACK
OSHA STANDS FOR OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION
OUTPUT AN ACTION CAUSED IN RESPONSE TO THE DIFFERENCE BETWEEN SETPOINT AND PROCESS VARIABLE
OUTPUT MODULES GENERALLY PLUG-IN DEVICES SUCH AS RELAYS THAT PROVIDE POWER HANDLING TO ENABLE PROCESS CONTROL; MODULES CAN BE EITHER BINARY (ON/OFF) OR ANALOG (CONTINUOUSLY VARIABLE) FOR CURRENT LOOP CONTROL
OVERSHOOT THE CONDITION WHEN TEMPERATURE EXCEEDS SETPOINT DUE TO INITIAL POWER-UP OR PROCESS CHANGES
OXIDIZING AN ATMOSPHERE THAT CONTAINS SIGNIFICANT AMOUNTS OF ACTIVE OXYGEN.

P CONTROL STANDS FOR 'PROPORTIONING' CONTROL
PARAMETER ANY SPECIFIC CHARACTERISTIC OF A DEVICE/CONTROL
PARITY ADDITION OF ALL THE BITS IN A WORD IS COMPARED TO THE PARITY BIT (EVEN OR ODD). IF THEY ARE BOTH THE SAME, THE DATA IS ACCEPTED, OTHERWISE IT IS REJECTED.
PB STANDS FOR PROPORTIONAL BAND
PCB STANDS FOR PRINTED CIRCUIT BOARD
PD CONTROL STANDS FOR 'PROPORTIONING CONTROL WITH RATE ACTION
PEAK LOAD THE MAXIMUM ELECTRICAL LOAD OR THERMAL LOAD REACHED DURING A SPECIFIC PERIOD OF TIME
PERCENT AUTHORITY GENERALLY COMMON WITH THE ADJUSTMENT OF RECEIVER CONTROLLERS WHICH DETERMINES THE EFFECT OF THE RESET SIGNAL OF THE SECONDARY TRANSMITTER AS A PERCENTAGE (%) OF THE SIGNAL OF THE PRIMARY TRANSMITTER
PHENOLIC A RESIN BASED TYPE OF HARD RUGGED PLASTIC THAT IS USUALLY USED IN INSULATING. PHENOLIC IS THE SAME AS BAKELITE.
PI CONTROL STANDS FOR 'PROPORTIONING CONTROL WITH AUTO-RESET'
PID CONTROL STANDS FOR 'PROPORTIONING CONTROL WITH AUTO-RESET AND RATE'
PLATINUM THE NOBLE METAL GENERALLY USED IN TYPES R & S THERMOCOUPLES
PNEUMATIC CONTROLS CONTROLS THAT RUN ON LOW-PRESSURE COMPRESSED AIR
PNEUMATIC FINISH POINT THE MAXIMUM AMOUNT OF PRESSURE (PSI) THAT WILL COMPLETELY COMPRESS AN ACTUATOR'S SPRING TO COMPLETE ITS STROKE. EXAMPLE: AN ACTUATOR WITH A SPRING RANGE OF 3 TO 8 PSI; '8' IWOULD BE CONSIDERED THE 'FINISH POINT'.
POSITION PROPORTIONING CONTROL OUTPUT THAT UTILIZES TWO RELAYS TO CONTROL AN ELECTRIC OR MOTORIZED ACTUATOR MOTOR
POTENTIOMETER A BALANCING BRIDGE WHICH IS USED TO MEASURE VOLTAGE; ALSO THROUGH THE USE OF A RESISTOR IS USED TO CONTROL A CIRCUIT(S)
PPM STANDS FOR PARTS PER MILLION
PPR SEE 'PULSES PER REVOLUTION'
PRESSURE DROP THE DIFFERENCE IN PRESSURE BETWEEN TWO POINTS IN A FLOW SYSTEM. THE PRESSURE DIFFERENCES ARE USUALLY CAUSED BY FRICTIONAL RESISTANCE TO FLUID FLOW IN A CONDUIT, FILTER, OR OTHER FLOW SYSTEM
PRIMARY LOOP THE OUTER LOOP IN A CASCADE SYSTEM
PROCESS VARIABLE ANY CHARACTERISTIC OR MEASURABLE ATTRIBUTE WHOSE VALUE CHANGES WITH CHANGES IN PREVAILING CONDITIONS; SOME COMMON VARIABLES ARE TEMPERATURE, LEVEL, PRESSURE, FLOW, HUMIDITY, ECT.
PROM STANDS FOR 'PROGRAMMABLE READ ONLY MEMORY'.
PROPORTIONAL BAND THE CHANGE IN INPUT THAT IS REQUIRED TO PRODUCE A FULL RANGE CHANGE IN OUTPUT DUE TO PROPORTIONAL CONTROL ACTION
PROTECTION TUBE A TUBE WHICH IS CLOSED AT ONE END IN WHICH A THERMOCOUPLE IS INSERTED INTO IN ORDER TO PROTECT THE THERMOCOUPLE FROM EXCESSIVE HEAT OR ABRASIVE MEDIUM; PROTECTION TUBES COME IN MANY VARIETIES & MATERIALS. SEE  PROTECTION TUBE SELECTIONS STARTING ON Pg.
PSIA STANDS FOR POUNDS PER SQUARE INCH ABSOLUTE
PSID STANDS FOR POUNDS PER SQUARE INCH DIFFERENTIAL
PSIG STANDS FOR GAUGE PRESSURE WHICH IS THE AMOUNT OF PRESSURE ABOVE ATMOSPHERIC PRESSURE
PSIS STANDS FOR POUNDS PER SQUARE INCH STANDARD
PSYCHROMETER MEASURES RELATIVE HUMIDITY
PULSE WIDTH ERROR THE DEVIATION IN ELECTRICAL DEGREES OF THE PULSE WIDTH FROM THE IDEAL VALUE OF 180 DEGREES.
PULSES-PER-REVOLUTION THE NUMBER OF PULSE INTERVALS OF AN OUTPUT SIGNAL FOR EACH REVOLUTION OF THE INPUT SHAFT.
PWB STANDS FOR PRINTED WIRE BOARD
PYROMETER TYPICALLY MEASURES HIGH TEMPERATURES UPTO 2,000 DEGREES F.
PYROMETRY SEE 'THERMOCOUPLE' OR 'RTD'

QUADRATURE THE TERM FOR TWO (2) NEARBY IDENTICAL PERIODIC SIGNALS WHEN THE PHASE DISPLACEMENT IS NOMINALLY 90 ELECTRICAL DEGREES.

RAM STANDS FOR RANDOM ACCESS MEMORY
RAM STANDS FOR 'RANDOM ACCESS MEMORY'
RAMPING SETPOINT SEE 'SETPOINT, RAMPING'
RATE AN ACTION THAT SENSES THE RATE OF CHANGE OF TEMPERATURE AND COMPENSATES TO MINIMIZE OVERSHOOT; ALSO 'DERIVATIVE'
RATE ACTION THE DERIVATIVE FUNCTION OF A PROCESS TEMPERATURE CONTROLLER
RATE TIME THE TIME INTERVAL OVER WHICH THE SYSTEM TEMPERATURE IS SAMPLED FOR THE DERIVATIVE FUNCTION
RC RESISTIVE / CAPACITIVE CIRCUIT, USED IN DIGITAL CIRCUITS TO ESTABLISH A TIME BASE.
REGULATE TO MAINTAIN A CONTROLLED VARIABLE AT OR NEAR ITS RANGE OR SETPOINT, DEPENDING UPON THE DEVICE
REHEAT WHEN HEAT IS ADDED TO COOLED OR HUMIDIFIED PRIMARY AIR OR RECIRCULATED ROOM AIR
RELATIVE GAIN AN OPEN-LOOP GAIN DETERMINED WITH ALL OTHER MANIPULATED VARIABLES CONSTANT, DIVIDED BY THE SAME GAIN DETERMINED WITH ALL OTHER CONTROLLED  VARIABLES CONSTANT
RELAY (MECHANICAL) AN ELECTROMECHANICAL DEVICE THAT COMPLETES OR INTERRUPTS A CIRCUIT BY PHYSICALLY MOVING ELECTRICAL CONTACTS INTO CONTACT WITH EACH OTHER
RELAY ( SOLID STATE) A SOLID STATE SWITCHING DEVICE THAT COMPLETES OR INTERRUPTS A CIRCUIT ELECTRICALLY WITH NO MOVING PARTS AT ALL
RELIEF DAMPER SEE 'EXHAUST DAMPER'
RESET TO RESET OR TO 'CLEAR'; AUTOMATICALLY ELIMINATES OFFSET OR DROOP BETWEEN SETPOINT AND ACTUAL PROCESS TEMPERATURE; ALSO 'INTEGRAL'
RESISTANCE TEMPERATURE DETECTOR SEE 'RTD'
RESISTIVE/CAPACITIVE CIRCUIT SEE 'RC'
RESTRICTOR (PNEUMATIC) A SMALL FITTING-LIKE PART THAT CHANGES THE VELOCITY PRESSURE OF THE AIR LINE TO STATIC PRESSURE. THE GENERAL SIZE OF RESTRICTORS ARE 0.005' OR 0.0075', AND CAN BE FOUND ON PG#_____ OF THIS CAPP/USA CATALOG
RETRANSMISSION ALLOWS THE TRANSMISSION OF A MILLIAMP SIGNAL CORRESPONDING TO THE PROCESS VARIABLE, TARGET SETPOINT, OR ACTUAL SETPOINT TO ANOTHER DEVICE SUCH AS A CHART RECORDER
RETURN AIR AIR THAT IS BEING RETURNED FROM THE HEATED OR AIR-CONDITIONED SPACE/ROOM, BACK  TO THE HEATER OR AIR CONDITIONER
REVERSE ACTING A DECREASE IN THE MEDIA THAT IS BEING SENSED CAUSES AN INCREASE IN OUTPUT
RF STANDS FOR RADIO FREQUENCY
RHEOSTAT VARIABLE RESISTOR
RMS STANDS FOR ROOT MEAN SQUARED
ROM STANDS FOR READ ONLY MEMORY
ROOFTOP UNIT A PACKEGED HVAC UNIT WHICH IS SPECIFICALLY DESIGNED TO BE MOUNTED ON THE ROOFTOP OF A BUILDING. ROOFTOP UNITS RANGE IN SIZE FROM FROM SMALL-SINGLE ZONE UNITS, TO LARGE CAPACITY UNITS WHICH SUPPLY AIR TO MULTIPLE VAV TERMINALS, ETC.
ROT STANDS FOR ROTATION
RPM STANDS FOR REVOLUTIONS PER MINUTE
RS STANDS FOR ROTARY SCALE
RS 485/422/232 STANDARDS RECOMMENENDED BY THE EIA FOR SERIAL DATA TRANSMISSION BETWEEN DIGITAL DEVICES AND PROCESS INSTRUMENTS.
RTD STANDS FOR RESISTANCE TEMPERATURE DETECTOR; AN RTD IS A RESISTIVE SENSING DEVICE THAT DISPLAYS RESISTANCE VS. TEMPERATURE CHARACTERISTICS, AND POSITIVE TEMPERATURE COEFFICIENT. SEE A WIDE-VARIETY OF RTD's STARTING ON Pg.____ OF THIS CATALOG
RUN TIME THE TOTAL AMOUNT OF RUNNING HOURS WHICH AN HVAC SYSTEM HAS BEEN RUNNING SINCE EITHER ITS INSTALLATION, OR ITS LAST PREVENTATIVE MAINTENANCE DATE

SAMA STANDS FOR THE SCIENTIFIC APPARATUS MAKERS ASSOCIATION.
SCR STANDS FOR 'SILICON CONTROLLED RECTIFIER'.
SECONDARY LOOP THE INNER LOOP OF A CASCADE SYSTEM
SENSIBLE HEAT SENSIBLE HEAT IS HEAT THAT CHANGES ONLY THE TEMPERATURE OF THE AIR WITHOUT A CHANGE IN THE MOISTURE CONTENT.  GENERALLY A CHANGE IN DRY-BULB THERMOMETER READINGS USUALLY INDICATE CHANGES IN SENSIBLE HEAT
SENSOR, IMMERSION SEE 'IMMERSION SENSOR'
SERIAL COMMUNICATIONS THE SENDING OR RECEIVING OF BINARY CODED DATA TO A SUPERVISORY DEVICE SUCH AS A PC (PERSONAL COMPUTER) OR PLC (PROGRAMMABLE LOGIC CONTROLLER)
SETPOINT, ACTUAL THE VALUE OF A CONTROLLED VARIABLE THAT THE CONTROL/CONTROLLER IS CURRENTLY ACTING UPON
SETPOINT, DEVIATION FROM THE NUMBER OF UNITS DIFFERENCE BETWEEN THE CURRENT PROCESS VARIABLE AND THE SETPOINT
SETPOINT, RAMPING A SETPOINT THAT IS DETERMINED BT THE RAMP FUNCTION OF A CONTROLLER WHERE OVER TIME THE CONTROLLER VARIABLE REACHES A DESIRED VALUE
SETPOINT, TARGET THE END POINT OF THE RAMPING/RAMP FUNCTION
SHEDS WHEN THE SIGNAL IS LOST---IN SERIAL COMMUNICATIONS
SINGLE-POLE/DOUBLE-THROW SEE 'SPDT'
SLIDEWIRE POSITION PROPORTIONING AN OUTPUT ALGORITHM THAT UTILIZES A SLIDEWIRE FEEDBACK SIGNAL TO DETERMINE THE ACTUAL POSITION OF THE ACTUATOR/MOTOR BEING CONTROLLED
SOLID STATE RELAY SEE 'RELAY ( SOLID STATE)'
SPAN THE DIFFERENCE BETWEEN THE START  & FINISH POINT OF A RANGE. FOR EXAMPLE: A RANGE OF 50 DEG. TO 100 DEG. = SPAN OF 50 DEG.; 60 TO 9 VOLTS = SPAN OF 3 VOLTS; 3 TO 8 PSI = SPAN OF 5 PSI.
SPDT SPDT OR SINGLE-POLE/DOUBLE-THROW IS A SWITCHING ACTION THAT 'MAKES' ONE CIRCUIT IMMEDIATELY UPON BREAKING THE OTHER
SPRING-RETURN A SPRING MECHANISM INSIDE  AN ACTUATOR WHICH UPON A LOSS OF POWER (POWER FAILURE) IMMEDIATELY WILL DRIVE THE ACTUATOR EITHER TO AN OPEN OR CLOSED POSITION
SQUAREWAVE A REPETITIVE WAVEFORM, USUALLY A.C., WHOSE SHAPE IS ESSENTIALLY SQUARE OR RECTANGULAR USUALLY WITH AN EQUAL DUTY CYCLE.
SS STANDS FOR STEAM SUPPLY, AND/OR THE ALLOY STAINLESS STEEL
SSR DRIVE A.D.C. ON/OFF SIGNAL OUTPUT FOR CONTROLLING A SOLID STATE RELAY
STAGED OUTPUTS THE SET-UP OF TWO ANALOG OUTPUTS, WHERE ONE ANALOG OUTPUT VARIES ITS SIGNAL OVER A PORTION OF THE PID OUTPUT RANGE, AND THE SECOND ANALOG OUTPUT THEN VARIES ITS SIGNAL OVER THE REMAINDER OF THE PID OUTPUT RANGE
STAND-ALONE CONTROL A CONTROL/CONTROLLER THAT DOES NOT REQUIRE SUPPORT FROM ANOTHER DEVICE OR SYSTEM
STATIC DISCHARGE UNDESIRABLE CURRENT RESULTING FROM THE DISCHARGE OF ELECTROSTATIC ENERGY
STATION ADDRESS A UNIQUE IDENTIFIER ASSIGNED TO A DEVICE OR DEVICES FOR COMMUNICATIONS PURPOSES
STATUS-PRESSURE CONTROL REGULATING THE AIR PRESSURE INSIDE OF A DUCT OR A ROOM IN RELATION TO A REFERENCE PRESSURE. GENERALLY CONTROLLED IN TERMS OF INCHES OF W.C. (WATER COLUMN)
STRATIFICATION LAYERS OF AIR AT DIFFERENT TEMPERATURES OF DIFFERENT VELOCITIES FLOWING THRU A DUCT OR PLENUM
STROKE LENGTH THE LINEAR DISTANCE IN WHICH AN ACTUATOR SHAFT MOVES

TARGET SETPOINT SEE ' SETPOINT, TARGET'
TDC TDC-2000 & TDC-3000 ARE COMPLETE COMPUTER-BASED PROCESS CONTROL SYSTEMS DEVELOPED BY HONEYWELL THAT PROVIDE THE MONITORING, CONTROLLING, & AUTOMATION OF A N INDUSTRIAL PLANT'S PROCESS CONTROL LOOP(s)/SYSTEMS
TE STANDS FOR TOTALLY ENCLOSED
TEAO STANDS FOR TOTALLY ENCLOSED, AIR OVER
TEFC STANDS FOR TOTALLY ENCLOSED, FAN COOLED
TEFLON MANUFACTURED BY DuPONT, TEFLON IS A FLUOROCARBON-BASED POLYMER THAT IS USED FOR THE INSULATION OF WIRES.
TEMPCO STANDS FOR 'TEMPERATURE COEFFICIENT'.
TENV STANDS FOR TOTALLY ENCLOSED, NON-VENTILATED
THERMOCOUPLE A TEMPERATURE SENSING DEVICE THAT IS CONSTRUCTED OF TWO DISSIMILAR METALS WHERIN A MEASURABLE & PREDICTABLE VOLTAGE IS GENERATED CORRESPONDING TO TEMPERATURE; SEE OUR WIDE-VARIETY OF THERMOCOUPLES STARTING ON Pg.____.
THERMOCOUPLE BREAK PROTECTION A FAIL-SAFE OPERATION THAT ASSURES DESIRED OUTPUT UPON AN OPEN THERMOCOUPLE CONDITION
THERMOCOUPLE DOWNSCALE BURNOUT THE JUMPER POSITION THAT DETERMINES WHETHER, WHEN A THERMOCOUPLE FAILS, ITS OUTPUT IS REPLACED BY A MILLIVOLTAGE WHICH WILL MATCH THE THERMOCOUPLE'S MINIMUM VALUE
THERMOCOUPLE UPSCALE BURNOUT THE JUMPER POSITION THAT DETERMINES WHETHER, WHEN A THERMOCOUPLE FAILS, ITS OUTPUT IS REPLACED BY A MILLIVOLTAGE WHICH WILL MATCH THE THERMOCOUPLE'S MAXIMUM VALUE
THERMOSTAT MEASURES AMBIENT TEMPERATURE AND CONTROLS OTHER DEVICES IN AN HVAC SYSTEM. THERMOSTATS COME IN A WIDE VARIETY AND ARE GENERALLY EITHER ELECTRIC-DELIVERED OR PNEUMATIC
THREE MODE CONTROL SEE 'CONTROL ACTION, PID'
THROTTLING RANGE (CONTROLS) THE CHANGE IN ANY VARIABLE SUCH AS TEMPERATURE, PRESSURE, ETC. REQUIRED TO CAUSE A CONTROLLER'S OUTPUT TO VARY A PRE-DEFINED RANGE.
THROTTLING RANGE (SYSTEM) THE AMOUNT OF CHANGE OF ANY VARIABLE SUCH AS TEMPERATURE, PRESSURE, ECT. NECESSARY FOR THE CONTROLLER TO DRIVE THE ACTUATOR(S) THROUGH THEIR COMPLETE STROKE(S)
TIME PROPORTIONING CONTROL A CONTROL ALGORITHM THAT EXPRESSES OUTPUT POWER ( 0-100% ) AS A FUNCTION OF PERCENT 'ON' VS. PERCENT 'OFF' WITHIN A PRESET CYCLE TIME
TIME PROPORTIONING OUTPUT A CONTROLLER OUTPUT THAT IS ASSIGNED BY SOFTWARE TO FACILITATE TIME PROPORTIONAL CONTROL (GENERALLY A RELAY, SSR, OR SSR DRIVE OUTPUT)
TORQUE TYPICALLY PRODUCES ROTATION OR TWISTING SUCH AS IN MOTORS
TOTAL PRESSURE TOTAL PRESSURE IS MEASURED BY THE SUM OF STATIC AND VELOCITY PRESSURE
TRACKING A PROCESS  CONTROLLER FUNCTION THAT DEFINES WHETHER THE LOCAL SETPOINT WILL TRACK THE REMOTE SETPOINT; WHEN THE CONTROLLER IS TRANSFERRED TO A LOCAL SETPOINT, THAT LOCAL SETPOINT VALUE WILL MATCH THE REMOTE PROCESS VALUE WHEN THE TRANSFER OCCURS
TRANSDUCER A DEVICE THAT CONVERTS ONE SIGNAL TO ANOTHER; EXAMPLE: CONVERTING A 4 TO 20 mA SIGNAL TO A 3 TO 15 PSI SIGNAL, AND VICE-VERSA
TRANSMITTER (2-WIRE) USED TO TRANSMIT DATA VIA A TWO WIRE CURRENT LOOP; A 2-WIRE TRANSMITTER IS LOOP POWERED. SEE OUR LARGE TRANSMITTER SECTIONS FOR HONEYWELL, FOXBORO, ROSEMOUNT, & DWYER TRANSMITTERS
TRANSMITTER (4-WIRE) USED TO TRANSMIT DATA VIA A CURRENT LOOP OR A DC VOLTAGE; A 4-WIRE TRANSMITTER USES 2 WIRES FOR DATA & 2 WIRES FOR POWER; SEE OUR LARGE TRANSMITTER SECTIONS FOR HONEYWELL, FOXBORO, ROSEMOUNT, & DWYER TRANSMITTERS
TRIAC A SOLID STATE SWITCHING DEVICE USED TO SWITCH ALTERNATING CURRENT SIGNALS ON & OFF; TRIAC CIRCUITS ARE ALSO REFERRED TO AS SOLID STATE RELAYS OR SSR's
TRIP POINT THE VALUE THAT DETERMINES WHEN THAT SET OF PID VALUES BECOMES ACTIVE
TRIPLE POINT TERM USED TO DESCRIBE SOLID, LIQUID, AND VAPOR PHASES WHICH ARE ALL IN EQUALIBRIUM AT THE SAME TIME SO THAT THERE IS A 'FIXED-POINT' TEMPERATURE OF THE MATERIAL THAT IS BEING MEASURED.
TRUE RMS OFTEN USED IN DETERINING THE POWER OF A SIGNAL BY A MULTIMETER, IT STANDS FOR THE TRUE ROOT-MEAN-SQUARE VALUE OF AN AC OR AC + DC SIGNAL.

UDC STANDS FOR 'UNIVERSAL DIGITAL CONTROLLER', WHICH IS A PROCESS TEMPERATURE CONTROLLER MANUFACTURED BY HONEYWELL. UDC'S COME IN SERIES 2000, 3000, 5000, 6000, & 9000
UL STANDS FOR UNDERWRITERS LABORATORIES, INC., ESTABLISHES STANDARDS FOR PRODUCTS
ULTRAVIOLET APPROXIMATELY 380 NANOMETERS BELOW BLUE LIGHT, ULTRAVIOLET OR 'UV' IS OFTEN DETECTED AS A PART OF THE FLAME IN BOILERS, BURNERS, OVENS, KILNS, AND INCINERATORS.
UPSCALE BURNOUT SEE 'THERMOCOUPLE UPSCALE BURNOUT'
UV STANDS FOR ULTRA-VIOLET

VA VOLT AMPERE
VAC VOLTS ALTERNATING CURRENT
VACUUM A PRESSURE THAT IS LESS THAN ATMOSPHERIC PRESSURE
VARIABLE AIR VOLUME ALSO REFERRED TO AS 'VAV', WHICH IS A SYSTEM THAT CONTROLS SPACE TEMPERATURE BY VARYING THE QUANTITY OF SUPPLY AIR RATHER THAN BY VARYING THE TEMPERATURE OF THE SUPPLY AIR
VARIABLE FREQUENCY DRIVE A DEVICE OFTEN REFERRED TO AS A SPEED DRIVE WHICH VARIES THE VOLTAGE TO AN ELECTRIC MOTOR TO VARY THE SPEED OF THE MOTOR
VAV SEE 'VARIABLE AIR VOLUME'
VDC VOLTS DIRECT CURRENT
VELOCITY POSITION PROPORTIONING A CONTROL METHOD WHERE VALVE POSITION IS DETERMINED BY CALCULATING THE AMOUNT OF TIME IT TAKES TO OPEN OR CLOSE A VALVE BY MOVING THE VALVE FOR A PORTION OF THAT TIME
VELOCITY PRESSURE PRESSURE THAT IS CAUSED BY AIR BEING IN MOTION, AND HAS  A DIRECT RELATION TO THE VELOCITY OF THE AIR
VENTURI CREATES NEGATIVE PRESSURE AND INCREASED GAS FLOW VELOCITY DUE TO THE WAY IT NARROWS AND THEN FLARES-OUT; A SECTION OF THE BURNER
VFD STANDS FOR VARIABLE FREQUENCY DRIVE
VITON EXTREMELY CHEMICALLY RESISTANT FLUOROPOLYMER USING PLASTICIZING AGENTS TO INCREASE FLEXIBILITY.

WATT DENSITY MEASURED IN UNITS OF WATTS PER SQUARE INCH, SUCH AS THE WATTAGE WHICH COMES FROM A SQ. INCH OF THE SURFACE OF AN ELECTRIC HEATER OR HEATER ELEMENT.
WET-BULB TEMPERATURE AIR TEMPERATURE THAT IS MEASURED BY A WET-BULB THERMOMETER AND THAT IS LOWER THAN DRY-BULB TEMPERATURE IN INVERSE PROPORTION TO THE HUMIDITY. HOWEVER, THIS DOES NOT APPLY WHEN/IF THE AIR IS SATURATED
WILD STREAM IN MIXING APPLICATIONS THAT REQUIRE MATERIALS TO BE MIXED TO A DESIRED RATIO, THIS IS THE ONE PART OF THE MATERIAL THAT IS UNCONTROLLED
WINDUP SATURATION OF THE INTEGRAL MODE OF A TEMPERATURE CONTROLLER DEVELOPING DURING TIMES WHEN CONTROL CANNOT BE ACHIEVED, WHICH CAUSES THE CONTROLLED VARIABLE TO OVERSHOOT ITS SETPOINT WHEN THE OBSTACLE TO CONTROL IS REMOVED

ZONE A SPACE OR MULTIPLE SPACES (USUALLY ROOMS) WITHIN A BUILDING WITH HEATING AND/OR COOLING REQUIREMENTS THAT ARE VERY SIMILAR SO THAT THE COMFORT CONDITIONS CAN BE MAINTAINED THROUGHOUT BY ONE SINGLE CONTROLLING DEVICE
ZONE CONTROL WHEN A BUILDING IS DIVIDED INTO SEVERAL ZONES, AND EACH ZONE CAN BE CONTROLLED INDEPENDENTLY
ZONED REHEAT PROVIDES ZONE CONTROL FOR AREAS OF UNEQUAL LOADING & SIMULTANEOUS HEATING OR COOLING OF PERIMETER AREAS WITH DIFFERENT EXPOSURES. HEAT IS ADDED TO (AS A SECONDARY PROCESS) TO PRECONDITIONED PRIMARY AIR OR RECIRCULATED ROOM AIR