The thesis contains the results of research aimed at improving the accuracy of measuring the temperature of short heat pulses.
The analysis of current state of development of methods and tools for measuring temperature, which are based on the use of the dependence of various physical phenomena on temperature, as direct temperature measurement is not possible, is carried out in the work.
In the dissertation work in the scientific plan the following results are received:
1. For the first time, a method of thermocouple identification by a radio pulse of current, which allowed to obtain a complete transient characteristic in contrast to other methods that use current for heating, which receive a decreasing front and then mathematically converted to an increasing front, is proposed. This method uses a radio current pulse to heat the thermocouple. By spreading the frequency of the heating signal and the reaction of the thermocouple, it became possible to isolate the slowly increasing signal of the thermocouple against the background of a high frequency signal that heats the thermocouple using analog filtering of the high frequency component by a notch filter;
2. For the first time was developed a method of thermocouple identification by determining the frequency response of a thermocouple using infra-low frequency current, which has an advantage over other methods due to the stability of obtaining time constant values. The peculiarity of this method is to create the total temperature by heating the junction of the thermocouple with an electric sinusoidal current. In this case, the voltage of the second harmonic is released on the terminals of the thermocouple, due to the heating of the thermocouple according to the Joule effect. Also, there is the first harmonic component, which is due to the voltage drop due to the ohmic resistance of the thermocouple wires and the action of the Thomson and Peltier effects, which are proportional to the first degree of the current flowing through the thermocouple. The ratio of the amplitudes of the output and input voltages on the second harmonic gives the frequency response. The difference of their phases on the second harmonic gives Phase response.
3. Improved methods for identifying the dynamic characteristics of the laser beam by creating a quasi-stage signal, which allows to obtain the mode of setting the thermoEMF signal at the output of the thermocouple.
4. The method of measuring the temperature of short thermal pulses is improved, which allows to compensate the dynamic measurement error in real time, by using the parameters obtained on the basis of identification of dynamic characteristics of the thermocouple in the system of thermal inertia compensation of the thermocouple. The peculiarity of this method is the use of time constants of the thermocouple to compensate its thermal inertia and, as a consequence, increase the accuracy of measuring the temperature of short thermal pulses. The time constants of the thermocouple will be obtained on the basis of the approximation of the frequency response of the thermocouple. The frequency response is obtained using the above method of identifying the dynamic characteristics of thermocouples. Each defined time constant characterizes the link of the delay of the first order. By including the inertia link in the feedback system of the system, the thermal inertia of the thermocouple, which is described by a certain time constant, is compensated. By connecting the links in series with the inertial link connected to the feedback, which corresponds to the time constant found, it is possible to fully compensate for the effect of thermal inertia of the thermocouple on the input temperature signal. This compensates dynamic error of thermocouple temperature measurement.
Keywords: temperature, thermal impulse, measurement, transient characteristic, bode plot, increase of accuracy, identification of dynamic characteristics, thermocouple.
