Temperature Gauge: A device used to indicate the temperature of an item being monitored. The display can be an analog dial or a digital readout. Common methods of measuring temperature include bimetallic strip (bending of which increases with temperature) and the thermocouple which produces an electronic voltage that depends on the temperature.
Things to Consider: ANALOG (BIMETAL THERMOMETER): Case (typically hermitically sealed stainless steel with 1″ to 5″ diameter); Window and ring (double strength glass or plastic); Accuracy in terms of percentage, plus or minus, of full scale, standard sizes should meet ASME B40.3 Grade A, pocket sizes should meet ASME B40.3 Grade 3; Measurement Range choices: dual scale degrees F and C, single scale degrees F or C; External reset to allow calibration to any specific temperature in the measurement range; Stem (typically 0.250″ or 0.125″ O.D. stainless steel in lengths from 2.5″ to 72″); Connection style (typically threaded 1/4 or 1/2 NPT or plain non-threaded); Environmental conditions (instrument is not suitable for sustained temperatures exceeding 200F (93C)); Vibrating applications require case to be silicone filled to protect instrument; Thermowells prevent instrument damage and facilitate removal from a process with media that are corrosive or under pressure; Shipping weight; Warranty DIGITAL (ELECTRONIC THERMOMETER): Input type, Number of inputs, C/F switchable, Resolution, Accuracy, Maximum temperature measurement, Display (typically 3-1/2 to 5 digits), Backlit LCD, Battery life, Battery type, Input connection type, Delta T1-T2 (temperature difference between two probe locations), Data hold, Min/Max capability, Data storage, Hi/Lo limits with beeper; Other features to look for: compact, Water resistant, degrees K, Switchable for 3 or 4 wire sensors, auto power off, waterproof, dustproof, data-logging, printer port, NIST calibration certificate, Rugged case, Included accessories, Warranty.
IR Temperature Transmitter. A device for the remote (non-contact) measurement of an object. The device optically senses the object’s thermal infrared radiation (IR) and converts that input to an electrical signal that can be used to operate an integrated digital or analog readout, or to control another device. These transmitters are ideal for measuring rapidly changing processes. Because they do not contact the object being measured, they can measure temperatures up to 3000 degrees Centigrade.
Things to Consider: Temperature range, Accuracy, Repeatability, Emissivity, Spectral response, Response time to 95% full scale, Outputs, Display (LCD or Backlit LCD), Resolution, Power requirements, Battery life, Minimum spot size versus distance, Aiming method (Visual or laser or through lens), Hi/lo alarm, Data storage, Switchable degrees F/C, Tripod mount, Other features: talking IR meter, printer output, free software, hermetically sealed optics, auto power down, emissivity compensation, mounting bracket for fixed installation, NEMA-4 enclosure for fixed installation, fiber optic cable; Warranty.
RTD Temperature Transmitter. A measurement device that converts an RTD (Resistance Temperature Detector) resistance measurement to a current signal that can be used to operate an integrated digital or analog readout, or to control another device. The RTD component, also called a resistance thermometer, is a temperature sensor that exploits the change in electrical resistance of some materials with changing temperature.
Things to Consider: Material of resistance element (platinum most popular because has linear response to temperature changes), Temperature coefficient (ohms per degree C), Nominal resistance (IEC standard is 100 ohms at 0 degrees C), Temperature range of application (Depends on mechanical configuration and manufacturing methods — RTD’s may be used from -270 to 850 degrees C), Physical dimensions or size restrictions, Accuracy (IEC 751 and/or DIN 43760), Response time, Measurement current and self heating, Stability, Vibration resistance, Temperature shock resistance, Pressure sensitivity, Self inductance from sensing current, Capacitance, Lead wire configuration: 2-wire, 3-wire, 4-wire, 2-wire plus loop; Warranty.
Thermocouple. A device consisting of the junction of two dissimilar metallic conductors, such as copper and iron, which generate different currents when subjected to the same temperature. When this junction is connected to a third substance, the thermocouple generates a resultant current that can determine the temperature of the third substance or control an associated device.
Things to Consider: Configuration, Available calibration, Temperature range, Thermocouple type (e.g. J: Iron-Constantan or T: Copper-Constantan or E/K/N — types have different max termperatures and chemical resistances) temperatures Insulation/sheathing type, Chemical resistance, Electrical grounding requirements, Abrasion resistance, Vibration resistance, Immersion capability, Diameter, Length, Response time, Compatibility with existing installation, Lead length, Extension wire availability, Bending capability, Dual element option, ANSI polarity (negative lead identification method), Warranty.
