Features of temperature measurement of short thermal pulses

Short thermal impulses are typical for the explosions, glowing combustion products, which are accompanied by high pressure and destructive force. The most suitable thermocouples for measuring temperature values of a high-speed thermal process are thermocouples with known dynamic characteristics, which record the value of the output EMF during the temperature change transient process. Hourly dependence of the input temperature is calculated by converting from the operator to hourly form or from the hourly dependence through the inverted convolution of the output signal with the pulse transient characteristic by numerical methods. Restoration of the values of temperature acting on them is done by EMF measured values processing using the well-known dynamic characteristics of thermocouples, which are suggested to be pre-determined in the form of magnitude and phase frequency response, by heating the thermocouple with a sinusoidal electric current of the appropriate frequency. To be able to implement the method of determining the characteristics of thermocouple dynamics, a model of the processes that occur in the thermocouple when electric current is passing through it is presented. The use of sinusoidal electric current to heat up the thermocouple leads to the appearance of a DC component and a component with second harmonic in the output of EMF. On the basis of the proposed model, the algorithm of obtaining the magnitude and phase frequency response of the thermocouple by means of determining the ratio of the amplitudes of the EMF variable of the thermocouple in the form of a composition at the double frequency of the input current to the amplitude of the second harmonic of the input current, obtained by means of elevation to the square of output EMF instantaneous values by the calculating method, is developed. The methodology was developed, a research system was created, and experimental samples of the fast thermocouples were made. The obtained dynamic characteristics allow, by applying the inverse function, to adequately measure the current temperature of thermal impulses using the data of the output thermal EMF of thermocouples.   Keywords: measurement; temperature; thermal pulse; thermocouple; dynamic characteristics; Nyquist plot.