Text version of the page

anti-reset See “anti-reset windup.” anti-reset windup The feature of aPID temperature controller that prevents the integral (automatic reset)circuit from functioning when thetemperature is outside the proportional band. This standard feature helpsstabilize a system. Also called “anti-reset.” Application layer (OSI Layer 7) Thehighest layer of the seven-layer OSI (Open System Interconnection) model where communication begins with a specific application that comm-unicates with another device orsystem. All application-specific functions occur here, such as userauthentication and addressing. An e-mail application or web browser areexamples of the application layer forexchanging data over the Internet. The Application Layer resides abovethe Presentation Layer. ASME American Society ofMechanical Engineers. ARP (Address Resolution Protocol)The TCP/IP protocol that converts an IP address into a physical hardware address, such as an address for an address for an Ethernet card. ASTM American Society for Testingand Materials. atmosphere The ambientenvironment. atmosphere(atm) A standard unit ofpressure representing the pressureexerted by a 760 mm (29.92 in.)column of mercury at sea level at 45 degrees latitude and equal to 1,000g/cm

W A T L O W

Application Guide catalog - 7347 Glossary

Alloy 405/426 Alloys made of 94.5percent nickel, two percentmanganese, one percent silicon and 1.5 percent aluminum (405), and 80percent nickel and 20 percent copper(426). They form thermocoupleextension wire conductors for use with Type C (W5Re/W26Re) thermocouples for applications under 870°C (1600°F). Type C is not an ASTM calibration. ambient temperature See“temperature, ambient.” Alloy 556 American Gas Association (A.G.A.)Independent testing laboratory thattests gas-related appliances andaccessories to ANSI standards, or to A.G.A. standards in the absence of anationally-recognized standard. Watlow now uses nationally recognized testing laboratories to ANSI standards for gas-relatedproducts, rather than A.G.A. American Wire Gauge (AWG)A standard of the dimensionalcharacteristics of wire used to conductelectrical current or signals. AWG is identical to the Brown and Sharpe (B & S) wire gauge. ammeter An instrument that measuresthe magnitude of an electric current.
® A multipurpose alloy thatexhibits good resistance to sulfidizing, carburizing and chlorine-bearingenvironments. Alloy 556 ampere (amp, A) A unit that definesthe rate of flow of electricity (current) in a circuit. Units are one coulomb (6.25x 1,018 electrons) per second.
® is aregistered trademark of Haynes International. analog A method of representing datausing the amplitude of a signal. Alloy HR160 Î (dc). anneal analog output To relieve stress in a solidmaterial by heating it to just below itsmelting point and then graduallycooling it to ambient temperature. Annealing usually lowers the tensilestrength while improving flexibility andflex life. Metals and glasses are commonly annealed. A continuouslyvariable signal that is used to represent a value, such as the process value or set point value. Typical hardware configurations are 0 to 20mA, 4 to 20mA or 0 to 5V
® A material that exhibitssuperior resistance to sulfides with good resistance in some salt bath applications. It is commonly used to make sensor probe sheaths. AlloyHR160 annunciator A visual display thatuses indicator lights to display theformer or existing condition of several items in a system.
® is a registered trademark ofHaynes International. ANSI American National StandardsInstitute. The United States government agency that defines and maintains technical standards. alpha (A) The temperature coefficientof the change in electrical resistance of a material measured inohms/ohm/°C. It indicates the basicchange in electrical resistance in amaterial for each °C in temperature.Alpha is a defining parameter for resistance temperature detectors(RTDs). For example, common alphasfor platinum RTDs are 0.00385
Glossary Ω / Ω /°C(DIN) or 0.003916 Ω / Ω /°C (JIS). alternating current ( Alumel Å )An electriccurrent that reverses at regular intervals, and alternates positive and negative values.
® An alloy made of 95 percentnickel, two percent aluminum, twopercent manganese and one percent silicon. It forms the negative conductorof ASTM Type Kthermocouples.Alumel
2 (14.22 psi). atmospheric pressure Pressure ingrams per square centimeter or pounds per square inch exerted by theearth’s atmosphere on bodies located within it.
® is a registered trademark ofthe Hoskins Manufacturing Company. ambient compensation See“compensation, ambient.” 189