Fine Diameter Thermocouples - OMEGA - #1

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www.omega.co.uk +44 (0)161 777 6611 60 Unsheathed Fine-Diameter Thermocouples Small enough to measure the temperature of a bee. Maximum Service Temperature Table 1 Fine Diamter Thermocouples OMEGA® fine-diameter thermocouples are used whenever fast, accurate temperature measurements are required. The fine wire diameters enable accurate temperature measurements without disturbing the base temperature of the body, in which the installation is made, by keeping heat transfer via the leads to a minimum. Also, the fine junction permits accurate “pin-pointing” of the measured values. They are available in wire sized ranging from 0.013mm to 0.81mm in diameter. All fine-gauge thermocouples are made from carefully selected materials. To ensure consistent thermoelectric properties, each pack contains thermocouples made from matched pairs of wire within the same batch number. When specified, several packs of thermocouples made from the same batch can be supplied at no extra charge. Response Time While thermocouple response is a function of medium of submersion, wire diameter, alloy type and temperature level, it is possible to use Table 2 as a guide for comparing the various wire size thermocouples. Table 1 lists maximum service temperatures for long term exposures of bare wire thermocouples. For very short exposure times, temperatures of the fine-gauge thermocouples can be as high as the permissible temperatures for the 0.8 mm diameter thermocouples. ** Do not expose to oxidising atmospheres. Response Time* Table 2 Wire Size Still Air 60 ft./sec Air Still H2O mm (inches) 427°C/38°C 427°C/38°C 93°C/38°C 0.025 (0.001) 0.05 sec 0.004 sec 0.002 sec 0.127 (0.005) 1.0 sec 0.08 sec 0.04 sec 0.381 (0.015) 10.0 sec 0.80 sec 0.40 sec 0.75 (0.813) 40.0 sec 3.2 sec 1.6 sec *The time constant is defined as the time required to reach 63.2% of an instantaneous temperature change. The data for Table 2 are obtained by measuring the time required for a Type J fine-gauge thermocouple to reach 63.2% of its final temperature when its junction is alternately exposed to two different temperature levels. In this case, the time constant was measured for exposures between 427°C and 38°C air between 93°C and 38°C water. The thermocouples are of the beaded junction type as shown. The bead diameter D is about 2.5 times the wire diameter d. The thermocouples are supplied in pack containing five individually mounted elements having 300 mm leads, except for platinum alloy thermocouples, which are supplied with 150 mm leads. Other lead lengths are available. Consult Sales Department for details. The negative leg is slightly shorter than the positive leg for easy identification. Convenient Pack of 5 Fast Response Diameters Down to 0.013 mm High Accuracy Pin-Point Measurements Low Heat Transfer Applications Thermocouple 0.13 mm 0.38 mm 0.51 mm 0.81 mm Type J** 315°C 371°C 371°C 482°C K 593°C 871°C 871°C 982°C N 593°C 871°C 871°C 982°C T 149°C 204°C 204°C 260°C E 315°C 426°C 426°C 593°C R,S - - 1450°C 1450°C B - - 1700°C 1700°C D d L ENLARGEMENT OF BEADED THERMOCOUPLE JUNCTION • biophysics • metal cutting research • gas chromatography • internal combustion engine temperatures • scientific instruments • medical research • chemical reactions • space vehicles • industrial heating and structural applications • cryogenics • plasma research • calorimetry • thermoelectric cooling • petro-chemical research Thermocouple Types J Iron/Constantan R Pt 13% Rh/Pt K CHROMEGA®/ALOMEGA® S Pt 10% Rh/Pt T Copper/Constantan B Pt 6% Rh/ E CHROMEGA®/Constantan Pt 30% Rh N OMEGA-P®, OMEGA-N® THERMOCOUPLES