FIELD: physics.
SUBSTANCE: first version discloses a thermoelectric converter having two thermocouples with the same nominal static characteristic. Thermoelectrodes of different thermocouples are made from wire with different concentration of doping elements and/or from wire with different nominal cross section, and/or from wire subjected to different types of preliminary thermal processing. The wires are put into a metal sheath made from heat-resistant steel or an alloy and are insulated from each other and from the sheath by a mineral insulation made from magnesium oxide or aluminium oxide. The invention discloses a structure of a thermocouple cable for making the thermoelectric converter in the first version, consisting of four wires made in pairs from two different thermoelectrode alloys. The wires made from the same thermoelectrode alloy are distinguished from each other by concentration of doping elements and/or nominal cross section and/or type of preliminary thermal processing. The second version discloses a thermoelectric converter consisting of a switching unit, a protective jacket, a thermocouple mounting unit having a through hole for mounting control or standard measurement apparatus inside the protective jacket, and two detecting elements in form of thermocouple with the same nominal static characteristic. The thermocouples are distinguished from each other by the type of materials insulating the thermoelectrodes and/or the cross section of the thermoelectrodes and/or concentration of doping elements in the thermoelectrodes and/or the type of their preliminary thermal processing and/or from the number of mechanical protection elements of the thermoelectrodes and its geometrical parametres. The method of determining the need to check or calibrate the thermoelectric converter involves use of thermocouples in the converter, having different degree of sensitivity to factors which cause changes in their static characteristic during use, which is defined as the difference between changes in characteristics of the thermocouple by a value not less than 0.15% from the measured temperature level in the calibration interval established using a method based on assumption of continuous variation of metrological characteristics of measurement apparatus with finite random speed. During use, readings of both thermocouples are taken simultaneously or after a time interval during which change in temperature does not exceed its measurement uncertainty, and the need to check or calibrate the thermoelectric converter is determined after divergence of the obtained results by a value greater than the expanded uncertainty of the difference between readings of the thermocouple.
EFFECT: more accurate measurement results, reliability of technological processes and quality of the product.
7 cl, 5 dwg, 4 tbl
