SU621995A1 - Device for determining material heat conductivity - Google Patents

Description

Tours (for example, a thermocouple) placed in the material under study, a pulsed heat source, the output of which is connected via a key and a pulse generator to a meter with indication and an amplifier, is introduced together with a temperature maximum moment determination unit a temperature conversion functional unit connected to the amplifier and but the output through the block of determining the moment of maximum is to the control input of the key.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 is a graph of voltage changes in a function block.

A device for measuring the thermal diffusivity of materials contains a pulsed heat source 1, a temperature sensor 2 placed in the material under study, an amplifier 3, a functional unit 4, a block 5 for determining the maximum time, a key 6, a pulse-7 generator and a counter 8 with indication.

The device works as follows.

When the pulsed heat source 1 is turned on, a thermal pulse is simultaneously sent to the temperature sensor 2, the material B is placed, and key 6 is opened. The generator 7 starts to send voltage pulses to meter 8 with indication and the number on the indicator display of the meter increases, starting with zero. The counter with indication can be executed on an integrated chip K145IP7B with IV-21 (HI).

The temperature of the material under study, measured by a sensor (for example, a thermocouple), gradually rises at a certain distance from the heat source, reaches its maximum value, and then begins to fall. The voltage removed from the temperature sensor is amplified by amplifier 3 (for example, integrated circuit IC 1UT-401B) and fed to functional unit 4. The functional unit can be performed on one semiconductor diode.

FIG. 2 explains the principle of operation of the functional unit 4. When a voltage t / Bx at the output of this block is applied to its input, the voltage t / out changes its value: it is really sharper and the precise determination of the maximum is no longer difficult. In addition, an abrupt change in voltage makes it possible to simplify the block 5 for determining the moment of maximum. It can be performed on a diode and a capacitor. At the moment of reaching the maximum temperature value, the block for determining the moment of maximum issues a signal to key 6 and closes it. When this generator 7 stops sending pulses to the counter 8 with the display. A figure is displayed on the indicator light panel, which is proportional to the thermal diffusivity of the material under study. The calibration of the proposed device is carried out by selecting the generator frequency. The proposed device is implemented on integrated circuits and has small overall dimensions and weight. Therefore, it is most useful when testing materials in the field.

Thus, the proposed device favorably differs from the known device, since its design is simpler, and the accuracy of measuring thermal diffusivity is higher due to a more accurate determination of the moment when the maximum temperature value is reached.

Claims (2)

1. Chudnovsky A. F. Thermophysical characteristics of dispersed materials. Fizmatgiz, 1962. 2. Kharlamov A. G. Measurement of thermal conductivity of solids, M., 1973, p. 102-104.