SU1150497A2 - Method of checking temperature-sensitive resistors - Google Patents

Abstract

METHOD OF TESTING THERMORESISTS on avt. St. No. 684341, characterized in that, in order to improve the verification accuracy by eliminating the influence of environmental conditions, the duration G of the current pulse is chosen from the ratio I, R C. T.1-S, where g is the average mass heat capacity of the thermoresistant thermosensitive material; mass of thermosensitive m thermistor element; D is the specific thermal resistance of the contact between the thermistor and the array in contact with it; S is the surface area of contact of the temperature-sensitive element with the surrounding array; S is the coefficient determining the degree of process deviation (L of the thermistor from the adiabatic heating, obtained experimentally.

Description

4ib

:;ABOUT

c | 1150A97 The invention relates to thermometry and can be used in the method of calibration of thermistors. According to the main auth. 1 68A341, a method is known for calibrating ternoreoretor jors by determining the characteristic of a thermoreistor when an electric current is passed through it and compared with a calibration characteristic to establish the correlation between the temperature dependence of the resistance and the electrical power supplied to it, with: A rectangular current pulse of the sample amplitude is passed through the thermistor: the voltage on the thermistor is measured at two points in time during the current pulse and From From (the known The xaipaKhistorics of the thermistor pj. jO The disadvantage of the known method is the low accuracy of the calibration due to the fact that the heating of the thermistor is omitted, because the duration of the mpl / 25s is not optimized. given by the thermistor during the test impulse to its environment, which leads to the possibility of additional error depending on the external conditions in which the thermistor is located. In addition, during the transition thermal temperature, the temperature of the co-switch of the resistor passes through its entire operating range. Therefore, in those cases when the thermistor is in conditions of high temperatures, close to the upper limit of its measurement, it is impossible to remove its calibration characteristic, as a result of which, under these conditions, there is a known method for calibrating the bob (not applicable 4). 45 verification by eliminating the influence of ambient conditions. The goal is achieved by choosing the current pulse duration from the ratio 50 - - R T – P8

with

- average mass heat capacity of the thermosensitive material of the thermistor;

- heat sensitive mass

ha of the thermistor element; im serv el ad he ci sa no en where ter tel wa where

eight " , . „At

(3)

AtjAt,

At the same time, the energy inherent in the thermosensitive element is determined by the relation R - the specific thermal resistance of the contact between thermal and thermal. resistor and in contact with the NIN array; S is the contact surface area of the temperature-sensitive element with the surrounding array; O is the coefficient determining the degree of deviation of the thermistor process from the adiabatic one, obtained experimentally. The choice of the optimal duration of the current pulse makes it possible to ensure that the heating of the temperature-sensitive mentor of the thermorestor is close to abathic, as a result of which the heat, all of the heat released in it, is spent on the increase in temperature and the accuracy improves. When a test impulse is passed on to heat a temperature-sensitive element, heat is consumed in the amount of Q, cm At ,, (1) s - the average mass heat capacity of the material of the heat sensing element; and -. mass of the heat-sensitive element; it, - heating the temperature-sensitive element when a current pulse is passed through. In the case of an adiabatic cascade of the electrical resistance in a thermo-sensitive element., Heat fit cm fit is obtained. ut, warming up the thermosensitive element in the absence of heat leaks into the array, i.e. in the case of adiabatic heating. Since the temperature is actually attained below the temperature, according to the adiabatic heating, there is an error, determined in accordance with the expression iz.R..S where I R, the amplitude of the current pulse} is the resistance of the temperature-sensitive element; duration of the test current pulse Y4. The specific thermal resistance of the contact between the thermistor and the array in contact with it is determined from the expression where E. is the total thermal resistance; S g contact area of the temperature-sensitive element. Finally, taking into account 3) and (5), an expression is obtained for the duration of the test current pulse - | -t15. The method is implemented as follows. From the foKa source, a current of a known magnitude is supplied to the thermostatic element of the IsHCTopa thermoresum, which does not cause heating of the HT3 resistor. The voltage drop across the temperature-sensitive element is measured, proportional to its 19 "resistivity at a given time. Then dramatically increase the flow rate on the teIi4 sensitivity & element of rectangular current of known magnitude. The amount of thermal energy applied is controlled by the pulse duration, at 7L this voltage drop across the temperature sensitive element at any given moment of current pulse transmission is proportional to its resistance. The amplitude of the voltage drop across the temperature sensitive element at the time of termination of the test pulse is recorded. In practice, the duration of the test current pulse usually does not exceed 3 ms. Thus, the initial (before the test superheat) and the final (at the end of the test superheat) resistance of the thermistor are determined. It is important that both values are measured with almost the same accuracy. Knowing them, according to the calibration table, the temperature of the test overheating of the thermal resistor is determined. Then, the ratio of resistances corresponding to a given test overheating is practically obtained and theoretical, and these two ratios are compared with each other, on the basis of which a decision is made about the accuracy of the thermistor. The use of the described method of calibration of thermoresistors allows to perform disassembly verification of both thermorestores that heat up the thermal contact with the design on which they are located and the thermistors that do not have 1f {x: direct test (og, contact with the medium, the temperature is measured). Offered method It allows to evaluate the methodological error of test calibration, reduce the number of measurements and simplify the calibration equipment, which greatly improves the accuracy of the calibration.

Claims (1)

METHOD OF TESTING THERMAL RESISTORS by ed. St. No. 684341, characterized in that, in order to improve the accuracy of verification by eliminating the influence of environmental conditions, the duration ΐ of the current pulse is selected from the relation where c is the average mass heat capacity of the thermosensitive material of the thermistor; m - mass of the thermosensitive * element of the thermistor; R is the specific thermal resistance of the contact between the thermistor and the array in contact with it; S is the contact surface area of the thermally sensitive element with the surrounding array; - coefficient determining the degree of deviation of the heating process of the thermistor from adiabatic, obtained experimentally. • 1150497