Technical Definitions: Temperature and Heating Glossary

Glossary

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A.G.A: Refer to "American Gas Association"
Abrasion Resistance: This is the ability of the material to withstand abrasion.
Absolute Zero: It is the lowest possible temperature on the thermodynamic temperature scale, at which the energy of the particle is zero. Absolute zero is zero on the Kelvin scale, which is equivalent to -273.15°C or -459.67°F.
AC (Å): Refer to Alternating Current
AC Line Frequency: This refers to the number of cycles measured in every second of an alternating current (AC) sine wave. AC line frequency is measured in Hertz (Hz), and 50 Hz or 50 cycles is set as a standard. The standard in the United States is 60 Hz.
AC/DC: This is both alternating and direct current. Accelerated Aging: This is a process of establishing a shelf life or lifespan of a product through series of tests where it may be subjected to aggravated conditions of humidity, heat, oxygen, vibration, radiation, sunlight, and so on.
Accuracy: This is a difference between the value measured by the instrument and the true value or the corresponding value. The accuracy of the sensor is measured on NIST (NBS) standards.
Action: Any change in process variables can affect the output of equipment. The response of this change is known as action. Refer to "Reverse Action and Direct Action".
Active Components: These are electronic devices whose properties are altered on the application of electric current. Transistors, diodes, and integrated circuits are active components.
Actual: This refers to the existing value of the variable that is controlled.
Address: It may be represented by various symbols such as a label, name, register, a location in the storage, location of a station in a communication network, or a register or other data destination or data source.
Advance®: It is a type of thermocouple alloy, which is a trademark of Harrison Alloys Company. It comprises 45% nickel and 55% copper, and is used as a negative conductor in ASTM Type E, J, as well as T thermocouples.
Alarm: This is any form of a visual and/or audible signal, which suggests that the process has fallen or exceeded above or below its set point. For instance, an alarm may produce a visual or audible signal to indicate the rise or fall in temperature.
Alarm Dead Band: The process signal is changed to return the alarm to a normal state or to activate it. This change is known as alarm dead band.
Alarm Delay: This is the time of lag that occurs before the activation of an alarm.
Alarm Hysteresis: This is a difference between the values, where an alarm may turn OFF from turning ON or turn ON from turning OFF.
Alarm Module
Alarm Silence: This feature helps disable the output of the alarm.
Alloy #11®: This is a registered trademark of Harrison Alloys. It is a type of compensating alloy, which is made of 1% nickel and 99% copper. Mainly used for making the negative conductor, the alloy is used along with pure copper to develop a thermocouple extension wire, which is used in ASTM Type S and R thermocouples.
Alloy 188®: This is cobalt - nickel - chromium - tungsten based superalloy, which possesses high strength, and can strongly resist corrosion and oxidation. The alloy also possesses excellent welding and forming characteristics, which make it an ideal choice for applications in the nuclear, aerospace, chemical, and process industries. Being a registered trademark of Haynes International, this alloy is also known as HAYNES® 188 alloy.
Alloy 203/225: The alloys of this type has either of the two compositions: two percent chromium (225) and 98 percent nickel or 10 percent chromium (203) and 90 percent nickel. They are used to create wire conductors or extension wire conductors for Type D thermocouples or W3Re/W25Re thermocouples that are designed for applications up to 400°F or 200°C.
Alloy 214®: It is a nickel-aluminum-chromium-iron alloy, which assures excellent oxidation resistance at high temperatures. It is also well known for its resistance against nitriding, corrosion, and carburization in chlorine-bearing atmospheres. Alloy 214® is mainly used for making sensor probe sheaths, and is a trademark of Haynes International.
Alloy 230®: It is a nickel-chromium-tungsten-molybdenum alloy, which possesses excellent welding and forming characteristics, as well as combines several beneficial features. This alloy exhibits brilliant oxidation resistance, strength, and thermal stability at high temperatures. It is used for creating sensor probe sheaths. Alloy 230® is a trademark of Haynes International.
Alloy 405/426: Alloy 405 has a composition of one percent silicon, two percent manganese, and 94.5 percent nickel. Alloy 426 is made of 20 percent copper and 80 percent nickel. Both these nickel alloys are known for their high ductility, and excellent oxidation resistance over their temperature range of use (<870°C (1600°F)). These alloys are widely used for making extension wire conductors for Type C (W5Re/W26Re) thermocouples.
Alloy 556®: It is a nickel-iron-cobalt-chromium alloy that assures brilliant resistance to carburizing, sulfides as well as chlorine-bearing environments. The alloy also has excellent welding and forming characteristics. It is a trademark of Haynes International.
Alloy HR160®: This is a cobalt-nickel-silicon-chromium alloy, which exhibits excellent resistance to corrosion attacks at high temperatures. The alloy can withstand temperatures up to 2200°F (1204°C), and exhibits brilliant resistance to sulfides. Alloy HR160® is a trademark of Haynes International and is used to create probe sheaths for sensors.
alpha (Î±): This is a temperature coefficient of resistance, which is measured in ohms/ohm/°C. It is the electrical resistance factor of a material, which changes for each °C in temperature. For pure metals, the value of alpha is positive, whereas it is negative for some elements, and near to zero for a few metal alloys. Alpha values are set for different resistance temperature detectors (RTDs). For instance, the values are 0.003916 â„¦/â„¦/°C (JIS) or 0.00385 â„¦/â„¦/°C (DIN) for platinum RTDs.
Alternating current (Å): It is an electric current that reverses its direction, and as a result, it may have negative and positive values. This reversal takes place at regular intervals.
Alumel®: It is an alloy comprising 95 percent nickel, two percent manganese and aluminum (each), and one percent silicon. This alloy is used for making thermocouple extension wire and a negative conductor for Type K thermocouple. Type K is an ASTM calibration. It is a registered trademark of Concept Alloys.
Ambient compensation: See "compensation, ambient."
Ambient temperature: See "temperature, ambient."
American Gas Association (A.G.A.): It is an American trade organization that represents natural gas companies, gas appliance manufacturers, and gas producers. The organization tests gas-related accessories and appliances to A.G.A standards and ANSI standards.
American Wire Gauge (AWG): This is a wire gauge system used in North America to ascertain dimensional characteristics of solid, round, non-ferrous, electrical current-carrying wires. It is also known as Brown & Sharpe wire gauge (B&S), and wire dimensions is provided in ASTM standard B 258.
Ammeter: This is an instrument used to measure the electric current in any circuit.
Ampere: It is defined as the rate of electric flow in any circuit. Ampere is the SI (International System of Units) unit to measure electric current, and equals the flow of one coulomb in a second. Coulomb is a charge carried by an ampere in a second. One coulomb equals to 6.25 x 1,018 electrons per second.
Analog: It a method of data representation of a signal in terms of physical quantities. This term is mainly used for representing electric signals. It may also be used for hydraulic, mechanical, pneumatic and other signals, too.
Analog Output: It is a variable signal that is employed to represent a set point value or a process value.
Annealing: It is a heat treatment process performed to remove internal stresses of a solid. Annealing helps improve the ductility of metals by reducing its toughness, thereby making it useable. In this technique, the metal is heated to a temperature below its melting point, and allowed to cool at ambient temperature. It is suitable for various types of glasses and metals.
Annunciator: It is a visual display used in various industrial systems to indicate the status of various active electric circuits and systems.
ANSI: It is an abbreviation of the American National Standards Institute, which oversees the development of consensus standards for processes, products, and systems in the United Status. ANSI also coordinates the American standards with worldwide standards, thereby ensuring worldwide acceptance for American products.
Anti-reset: Refer to anti-reset windup.
Anti-reset Windup: This is also known as anti-reset, and is a situation or phase in a PID temperature controller that helps stabilize the system. In this, the controller resets the circuit and prohibits it from functioning if the temperature goes beyond the proportional band.
Application Layer (OSI Layer 7): The Application Layer is the layer of the seven-model Open Systems Interconnection (OSI) model and it is present over the Presentation Layer. Application Layer (OSI Layer 7) is the highest layer of the OSI model. It comprises protocols that focus on different process-to-process communication across the network, as well as assures a reliable communication interface. Web browser or email applications are the examples of this layer, and they ensure data exchange on the internet.
ARP: This is an abbreviation for Address Resolution Protocol, which is a low-level TCP/IP protocol that helps identify the physical address of a device as well as media control address (MAC) address, thereby enabling swift communication between devices on a local area network (LAN).
ASME: This is an abbreviation for the American Society of Mechanical Engineers. This is a multidisciplinary engineering organization that is involved in training and professional development, development of codes and standards, education, research, publications and conferences, and government relations. This non-profit organization conducts several technical conferences every year, and is also known for its technical publishing operations.
ASTM: This is an abbreviation for the American Society for Testing and Materials. It is a well-known organization that develops as well as publishes technical standards for a variety of services, materials, systems, and products. The organization mostly publishes voluntary consensus standards that operate internationally.
Atmosphere: This is a gaseous envelope covering the earth.
Atmosphere (atm): It is the standard pressure or a reference pressure, which is equal to the atmospheric pressure at the level of the sea. The value of standard pressure is 101 325 Pa or 1.013 25 bar. It is basically a pressure exerted by 29.92 inches (760 mm) of mercury at sea level. This measurement is in reference to tests conducted at the latitude of 45 degrees.
Atmospheric Pressure: This is also known as barometer pressure, and is measured as pounds per square inch or grams per square centimeter. It is basically the pressure within the earth's atmosphere or other planets.
Automatic Mode: This is a feature of a PID controller that allows setting the output controls according to the set point and the process variable (PV).
Automatic Power Reset: This is a feature in controllers where the output is not affected with a power outage. The output is automatically re-energized after the power restoration. This automatic re-energization of output is affected by temperature. It will work perfectly as long as the temperature remains in controlled limits.
Automatic Prompts: These are microcontroller-produced data entry points, where the user is informed to enter a proper control value.
Automatic Reset: This is an important function of a PID temperature controller or a PI temperature controller, where the temperature of the process is set after the stabilization of the system.
Auto-tune: It is a feature of a PID controller that automatically sets its temperature control values to match a specific thermal system.
Auxiliary Output: This output is independent of the primary control output, and it controls activities that may not be part of the primary control output. This may include activities of devices such as buzzers and lights, gas purges, door latches, etc.
AWG: Refer to "American Wire Gauge".