The maximum deviation in a set of measurements between the temperature indicated by a radiation thermometer and the known temperature of a reference source, including the uncertainty of the reference temperature source. The accuracy can be expressed in a variety of ways including temperature, percentage of temperature reading, or percentage of full scale temperature of an instrument.
The AMS2750 standard was created to provide a consistent specification for temperature control throughout the aerospace supply chain. The standard covers pyrometric requirements for thermal processing equipment used for heat treatment. It covers temperature sensors, instrumentation, thermal processing equipment, system accuracy tests, and temperature uniformity surveys. These are necessary to ensure that parts or raw materials are heat treated in accordance with the applicable specifications.
Precipitation hardening, also called age is a heat treatment process that produces uniformly dispersed particles (precipitates) within a metals grain structure. These particles hinder dislocation motion and thereby strengthen the metal, particularly those that are malleable. Often preceded by a solution treatment cycle.
The temperature of the air surrounding the instrument, as well as radiant temperature from other sources.
A thermocouple constructed from low cost materials typically copper, nickel and iron. Examples of base metals thermocouples are K type, N type, T type J type and E Type.
Annealing is a heat treatment that alters the properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature and then cooling (normally slowly for steel).
American Society for Testing and Materials.
In brazing, the filler metal melts at a higher temperature than in soldering, but the work piece metal does not melt. The difference between brazing and soldering is that brazing is undertaken at temperatures greater than 450 °C and soldering less than 450 °C.
The product is typically stationary for the duration of the process, loading and unloading through the same door. They vary in size depending on product being processed from table top to room sized.
A procedure that is performed to determine and set the parameters affecting an instrument's performance in order to ensure its designed accuracy within prescribed limits.
The temperature scale in which the temperature in Celsius (TC) is related to the temperature in Kelvin (TK) by the formula; TC = TK - 273.15. The freezing point of water at standard atmospheric pressure is very nearly 0°C, and the corresponding boiling point is very nearly 100°C.
Heat transfer due to bulk movement of molecules within fluids such as gases and liquids. Many low temperature processes will used forced air to increase convection and so transfer heat faster to the product
This heat treatment is a case or surface hardening process. it involves surrounding steel or iron with a carbon rich material or atmosphere. The intent is to increase the carbon content of the material being processed so that higher hardness can be achieved. Adjusting carburising time and temperature give different levels of diffusion and therefore different case depths.
Any oven with a mechanism to transfer product or material through the oven. Popular types include mesh belt, roller hearth, rotary hearth and walking beam. Reflow soldering and paint curing ovens also fall into this category.
The inverse of an error in relation to the calibration of an instrument, thermocouple or other device. If the error is 0.1 °C the correction factor is -0.1 °C.
Cure schedule is the time and temperatures specified to complete either a chemical linking or evaporation resulting in a tighter linkage and hence tougher coating.
Two or more electrical conductors connecting several transmitters and receivers of digital data.
The German standard for many instrumentation products.
The change in instrument indication over a period of time not caused by external influences on the device.
Electro-Magnetic Interference/Radio Frequency Interference, which affects the performance of electronic equipment.
Emissivity is defined as the ratio of the energy radiated from a material's surface to that radiated from a blackbody (a perfect emitter) at the same temperature and wavelength and under the same viewing conditions. Emitted energy indicates the temperature of the object. Emissivity can have a value from 0 (shiny mirror) to 1.0 (blackbody).
A rating given (usually by agencies and regulatory bodies) to indicate the severity of the environment in which the unit will function reliably.
Temperature measurement scale where, at standard atmospheric pressure, the freezing point of water is 32°F and the vaporization point of water is 212°F. To convert from Celsius, use F = (C x 1.8) + 32.
The temperature measurement accuracy expressed as a percentage of the maximum possible reading of an instrument.
Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, normalizing and quenching.
A device that absorbs heat while remaining at a steady temperature. Typically a sealed solid to liquid system based on phase change materials.
The point at which the two wires of a thermocouple are joined together. This is typically a welded junction free of impurities the size of which is kept small to enable a point measurement to be taken.
A European organization that coordinates and sets related standards among the European Community.
The property of a material to resist the flow of electrical current and expressed in Megohms as the ratio of an applied electrical potential divided by the flow of electrical current resulting there from.
Insulation is the process of keeping heat, sound, or electricity from spreading. It's also the material used to do so.
Grades of intrinsic safety protection pertaining to enclosures per the British Standard 4752. The type of protection is defined by two digits, the first relating to accessibility and the second to environmental protection. The two numbers are preceded by the letters IP.
A temperature scale that is directly related to the heat energy within a body. Formally, a temperature scale in which the ratio of the temperatures of two reservoirs is equal to the ratio of the amount of heat absorbed from one of them by a heat engine operating in a Carnot Cycle to the amount of heat rejected by engine to the other reservoir. The temperature of the triple point of water (in this scale) is defined as 273.16°K. To convert from Celsius use formula: K=C+273.16.
Defines the speed at which product or material is passing through a conveyorized oven. Units of measure vary depending on process.
As used in the food industry the term refers to the calculation used to determine the number of times the population of a target micro-organism has been reduced. The F0 calculation is commonly used in sterilization processes carried out at 121C.
A type of primary or non-rechargeable cell with a very high energy density. Lithium cells have very low self-discharge and find application in devices where battery life can be measured in years. Some lithium cells can be used at high temperatures so they are often used to power thermal data loggers.
A type of secondary or rechargeable cell in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging. They have limited ability to work at temperature and are limited to applications at less than 55C. main use in portable electronic equipment such as phones and computers.
Microporous materials are very efficient insulation products. These products actually have thermal conductivity values lower than still air. This performance is based on the ability of microporous insulation to block the three modes of heat transfer (i.e., conduction, convection, and radiation).
NiMH stands for Nickel-Metal Hydride. Unlike other cells NiMH cells do not use heavy metals that may have toxic effects. In addition, they can store up to 50% more power than NiCad batteries and do not suffer from memory effects.
Calibration in accordance with and against standards traceable to NIST (National Institute of Standards and Technology, USA). Traceability to NIST is a means of ensuring that reference standards remain valid and their calibration remains current.
Normalizing as a process involves heating a steel above the critical temperature, holding for a period of time long enough for transformation to occur, and air cooling. This type of heat treatment establishes a more uniform carbide size and distribution which facilitates later heat treatment operations and produces more uniform properties in the final product.
A thermocouple constructed from precious metals typically platinum and rhodium. There are three types in common use Type B type R and Type S.
At temperatures above its transition temperature, phase change material begins to soften and flow. This phase change requires energy and so a PCM absorbs the heat energy during the phase change with an increase in temperature.
A term use in the thermal profiling industry to describe a file containing information related to the oven or furnace and product produced but not the temperature data. It provides a template to superimpose on the data and relates position in the process to temperature measured.
A broad class of temperature measuring devices, originally designed to measure high temperature, but some are now used in any temperature range. Includes radiation pyrometers, thermocouples, resistance pyrometers, and thermistors.
The degree to which a single instrument gives the same reading on the same object over successive measures under the same ambient and target conditions. The ASTM standard E 1256 defines it as the sample standard deviation of twelve measurements of temperature at the center of the span of the instrument. Generally expressed as a temp difference, percent of full scale value, or both.
Relative humidity (RH) is a measure of the amount of water vapour present in the atmosphere compared to the amount required to saturate that atmosphere at the same temperature; normally expressed as a percentage.
See Temperature Resolution, Optical Resolution, or Spatial Resolution.
The time for an instrument output to change to 95% of its final value when subjected to an instantaneous change in target temperature corresponding to the maximum temperature the instrument can measure (per ASTM E 1256). The average time required for software computation within the processor is also included in this specification for Ircon products.
A recommended standard developed by EIA that is an improvement over RS-422 in that it allows an increase in the number of receivers and transmitters permitted on the line.
The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference. The voltage measured is composed of two parts one generated at the junction of the conductors and the other along the part of the conductor where the temperature gradient exists. This effect is the method by which thermocouples work and each thermocouple type will have a different Seebeck voltage versus temperature curve.
Soldering is a process in which two or more items (usually metal) are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering and brazing are very similar.
Is a standard methodology for measuring process stability and capability in manufacturing industry. Process or product measurements are taken in time during the manufacturing process and plotted on a graph along with control limits. This provides graphical and numerical indication of the process capability.
The ambient temperature range an instrument can survive in a non-operating Range mode and perform within specifications when operated.
The SAT is performed by monitoring and recording data at a stable temperature and comparing the readings generated by the furnace control system and a reference system. The purpose of the test is to detect and quantify any deviation in furnace instrumentation accuracy and determine if the deviations are within acceptable limits.
The ideal temperature profile for a given process and product. This will depend on metallurgical requirements in the metals heat treatment industry and cure schedule provided by the coating manufacturer in the coatings industry.
A TUS is a test undertaken to determine the range of temperatures present at different locations in the furnace under normal operating conditions. This involves determining temperature variations by surveying at the maximum and minimum operating temperatures and at a series of intermediate temperatures. The location of the measurement points define the ‘working zone’ of the furnace.
A product designed to reduce thermal energy flow to a minimum; typically to protect temperature sensitive items from temperature extremes. Thermal barriers usually incorporate a combination of insulation and phase change materials.
Defined as the time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. Normally measured in units of W/mK. Insulating products will have very low values of thermal conductivity.
Thermal mass is the ability of a material to absorb and store heat energy. A lot of heat energy is required to change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to have high thermal mass. Lightweight materials such as timber have low thermal mass.
A set of time-temperature data points typically associated with the measurement of temperature in an oven, furnace or kiln. Temperature profiles can be taken from the product being processed or the ambient temperature in the process.
A lower grade and lower cost thermocouple wire that is used to connect the thermocouple grade wire to eth the measuring instrument. It is used in lower temperature enviroments where lower grade will not adversely affect system accuracy.
Teflon® is a brand name and a registered trademark of DuPont.
A property of an object which determines the direction of heat flow when the object is placed in thermal contact with another object (i.e., heat flows from a region of higher temperature to one of lower temperature).
The change in accuracy of an instrument with changes in ambient temperature from that at which the instrument was calibrated. Usually expressed as the percent change in accuracy (or additional error in degrees) per change in ambient temperature. For a rapid change in ambient conditions, refer to Thermal Shock.
The minimum simulated or actual change in target temperature that gives a usable change in output and/or indication.
See Temperature Coefficient.
An error due to a rapid change in the ambient temperature of an instrument. Expressed as a maximum error and the time required for performance to return to prescribed specifications.
A semiconductor material whose resistivity changes with temperature.
A number of similar thermocouples connected in series, arranged so that alternate junctions are at the reference temperature and at the measured temperature, to increase the output for a given temperature difference between reference and measuring junctions.
A thermocouple created from the junction of platinum-rhodium 30% and platinum-rhodium 6% conductors. This thermocouple has been developed for use at very high temperature. It is very stable and used protected in a ceramic tube.
A graphical representation of the acceptable limits within which the temperature profile must fall.
The condition of temperature and pressure under which the gaseous, liquid, and solid phases of a substance can exist in equilibrium. For water at atmospheric pressure, this is typically referred to as its freezing point.
A thermocouple created from the junction of nickel/chrome and constantan. It is very stable but upper temperature is lower than type K and N so use is not as widespread. IEC color coded violet and ANSI violet.
A thermocouple created from the junction of iron and constantan and widely used, it has a smaller temperature range than the Type K but similar costs. Care is needed when using in oxidizing environments as the iron wire will corrode. IEC color coded white and ANSI black.
Type K is the most commonly used thermocouple it is comprised of one conductor of Alumel and the other of Chromel. Used over temperature range of 0C to 1370C. IEC color coded green and ANSI Yellow
A thermocouple created from the junction of Nicrosil and Nisil conductors. It was developed to tackle the problem of accuracy drift seen in type K thermocouples exposed to high temperatures for long duration. It is often used in aerospace industry when conducting temperature uniformity surveys. IEC color coded orange and ANSI pink
A thermocouple created from the junction of platinum and platinum/rhodium conductors. The rhodium content is 13%. It is very stable and used at very high temperatures often protected in a ceramic tube the high level of rhodium makes this an expensive thermocouple.
A thermocouple created from the junction of platinum and platinum/rhodium conductors. The rhodium content is 10%. It is very stable and used at very high temperatures often protected in a ceramic tube marginally lower cost than type R.
A thermocouple created from the junction of copper and constantan conductors, it is very stable and repeatable. Typically used at cryogenic temperatures it finds wide use in the food processing industry. IEC color coded blue and ANSI blue.
Confirmation of a design with regard to performance within all prescribed specifications.
A test where oscillatory or repetitive motion is induced in an object (as per MIL-STD-810 or IEC 68-2-6), which is specified as an acceleration in ±gs and power spectral density (PSD), after which the unit is tested for proper operation.