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Compensation conductor should be use to guide _ instrument

by:JVTIA     2020-10-28
Method of commonly used has the following several kinds of freezing temperature compensating conductor thermoelectric potential correction coefficient method of the cold end temperature compensator method p-n junction compensation method cold end extension method. One s type thermocouple measured thermoelectric potential is 2934 mu V, the cold end temperature of Tn = 30 oc, strives for the measured temperature T. Solution: check the EAB ( 30, 0) =1203μVEAB( T, 0) =EAB( T, 30) +EAB( 30, 0) = 2934 + 1203 = 4137 mu V look-up table the EAB ( T, 0) =4137μV,T=101oC. When the temperature of the cold end To = Tn To 0 oc, as long as Tn constant, known by fixed a EAB ( Tn,0oC) , transfer the measured value to the cold end temperature of 0 o the thermoelectric potential of C. Connect with the free cod of a s type thermocouple should be convenient and reliable; Protect casing thermal electrode should ensure sufficient isolation and harmful medium. Two hot electrode welding of thermocouples must be strong; Two hot electrode should be well insulated between each other, prevent short circuit; Non-standard thermocouple or on the order of magnitude less than the range using standardized thermocouple, generally no unified indexing table, mainly used in some special occasions. S type thermocouple cold end temperature compensation as a result of the thermocouple materials are generally more expensive ( Especially when using precious metals) And temperature measuring points are far away the distance to the instrument, and in order to save thermocouple materials, reduce cost, usually adopt the compensating conductor (of the cold junction of the thermocouple The free end) Reaches to the relatively stable control indoor temperature and connected to the meter terminals. It must be pointed out that the role of the thermocouple compensation wire only extend thermal electrode, make moves to the control room of the cold junction of the thermocouple meter terminal, it itself does not eliminate the cold end temperature change on the influence of temperature, no compensation. A variety of s type thermocouple relationship between temperature and thermoelectric emfs indexing table is made in the cold end temperature is zero, therefore, when using a thermocouple temperature measurement, if you want to direct application of thermocouple indexing table, you must meet the t0 = 0 ℃ condition. In this way, not only is not 0 ℃, and is not a constant, because the t0 this would introduce errors. Eliminate or can the error compensation method.
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