SU1486896A1 - Device for thermal analysis - Google Patents

Description

The invention relates to thermophysical measurements, in particular to thermal analysis. The purpose of the invention is to improve the measurement accuracy. The device contains a furnace, program master, adder, regulator,

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sample block, sample and medium temperature sensors, two large-scale amplifiers, two analog memory blocks, two drivers, two voltage difference amplifiers, a differentiator, a comparator, a controlled key and a recording system. During the course of a phase transformation, a change in the temperature difference between the medium and the sample using a differentiator, comparator amplifiers and a key causes a change in the mode of operation of the regulator so that the current temperature difference is maintained, which is the mode of operation during transformation before its completion, after In this case, the heating mode allows one to accurately determine the temperature range of the pre- P sample rotation. 1 il. TO

The invention relates to a technique for thermophysical measurements.

The purpose of the invention is to improve the measurement accuracy by changing the mode during the conversion of linear heating to heating with a given temperature difference between the medium and the sample surface.

The drawing shows the block diagram of the device.

The device contains a furnace with 1 software unit 2, an adder 3, a regulator 4, a unit 5 for placing a sample, a sensor 6 for the surface of the sample, a sensor 7 for medium temperature, the first! 8 and the second 9 large-scale amplifiers, system 1 (3 registrations, differentiator 11, the first analog memory block 12, the logic comparator 13, the first voltage difference amplifier 14, the first driver 15, the second analog memory block 16, the second voltage difference amplifier 17, the second driver 18, and the controlled switch 19.

The device works as follows, at once.

Unit 2 linearly increases the output signal, which, after the totalizer 3 subtracts the reverse signal

connection (sensor signal 7 temperature

Wednesday) is fed to the input of the regulator

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4, controlling the furnace 1. Thus, the regime of linear heating T _с = ν -С is realized (where T _с is the medium temperature; ν is the heating rate; С is time). In the absence of transformations in the sample, the signals at the outputs of devices 12 and 16 of analog memory are slightly different from the signals at their inputs, the signals at the outputs of drivers 15 and 18 are missing. As a result, there is no signal at the output of the logic comparator 13. With insufficient control of the control law, for example, caused by voltage fluctuations in the supply network or changes in the heat exchange conditions of the unit and the furnace, signals sufficient to form can appear at the inputs of amplifiers 14 and 17 signals shaper 15 and 18. But these signals have the same polarity. For example, increasing the supply voltage causes a short-term increase in power consumed for heating. Then both the temperature difference between the medium and the sample and the heating rate increase, which leads to an increase in signals at the outputs of the second large-scale amplifier 9 and differentiator 11. The analog memory devices 12 and 16, after a time shift, output the differences to the amplifiers 14 and 17 , the two voltages are positive signals, .a formers. 15 and 18 form the "+1" signals. As a result, the logic comparator 13 does not work and the linear heating mode continues. The device works similarly when the supply voltage drops and when the heat exchange conditions between the unit and the furnace change.

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When an exothermic transformation proceeds in a sample, the heating rate of the sample increases, and the temperature difference between the sample and the medium decreases. Then the differentiator

II dramatically increases the output signal, and the second large-scale amplifier

9 reduces it. As a result, the first driver 15 generates a “+1” signal, and the second driver 18 - “-1”. The logic comparator 13 does not work again and the linear heating mode continues, which is preferable during the exothermic transformation in the sample than the heating mode given temperature difference.

During the endothermic transformation in the sample, the heating rate of the sample decreases, and the temperature difference between the medium and the sample increases. Differentiator 11 sharply reduces its signal, while the second scale amplifier 9 increases it. The devices 12 and 16 of the analog memory, having performed the motion in time for time T, will give the first inputs of the amplifiers 14 and 17 the difference of two voltages, the signals corresponding to the moment of time before transformation. The second inputs of the amplifiers 14 and 17 of the difference between the two voltages receive signals corresponding to the flow

20 transformations. After amplification, the first driver 15 generates a signal Ϊ ", and the second driver 18 -" +1 ” _O Logical comparator 13 breaks the inputs of the devices 12 and 16 analog

25 memory, switches the setting device 2 to the tracking mode of the sensor signal 7 of the medium temperature and switches the input -> controller 4 to the output of the second amplifier 17 of the difference of two voltages. In that

30 case, the controller 4 provides heating in a mode in which the signal at the first input of the second amplifier 17 of the difference of two voltages is equal to the signal at the second input of the same amplifier, i.e. the equality of the current temperature difference between the medium and the sample and the magnitude of the temperature difference at the instant of operation of the logical comparator 13 (the beginning of the transformation) is maintained. This means a smooth transition from the linear heating mode to the heating mode to the specified temperature difference between the medium and the sample. This position is maintained on pro45. over the entire conversion, since the first input of the logic comparator 13 continues to receive a signal ^and -1 ". After the conversion is complete, the heat flux coming to the ob 5θ particle causes it to heat up quickly and increase the signal of the differentiator 11 to the former (before the conversion) value. As a result the output of the first driver 15 "-1" disappears,

55 and with it the signal at the output of the logic comparator 13 disappears. The devices 12 and 16 of the analog memory go into tracking mode, the signal 5 is sent to the input of controller 4

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torus 3, and setpoint 2 continues to linearly increase its output signal from a value that corresponds to the temperature of the end of the transformation. The device smoothly passes into a linear heating mode.

The device allows to increase the accuracy of determining the temperature range of the sample transformation and bring it to the accuracy of the sample temperature measurement in the absence of transformations

Claims (1)

Claim A device for thermal analysis, containing a furnace, a unit with a cavity for placing a sample, temperature sensors of the medium and sample surface, a software setting device, an adder, a regulator, a first large-scale amplifier whose input is connected to a sample temperature sensor, a second large-scale amplifier whose inputs are connected to sensors medium and sample temperatures, and a recording system, characterized in that, in order to improve the accuracy of the analysis, it additionally contains a differentiator, the first and second blocks of analog memory, logical to mparator first and second formers, the first and second voltage difference amplifiers and controllable the key, while the input of the differentiator is connected to the output of the first large-scale amplifier, the input of the first block of analog memory is connected to the output of the differentiator, and the control input to the output of the logic comparator, the first input of the first amplifier of the voltage difference is connected to the output of the analog memory, and the second input - with the output of the differentiator, the input of the first driver is connected to the output of the first amplifier of the voltage difference, the input of the second unit 15 analog memory is connected to the output of the second scale amplifier, and the control input is connected to the output of a logic comparator, the first input of the second voltage difference amplifier is connected to the output of the second analog memory block, and the second input is connected to the output of the second scale amplifier; the input of the second driver is connected to the output the second amplifier of the voltage difference, the first input of the logic comparator is connected to the output of the first driver, the second input with the output of the second driver, and the output - to the control input of the generator, n rvy controllable switch input connected to the output of the adder, the second input - with the output of the second voltage difference amplifier control input - to the output 35 comparator, and the output - with the input of the regulator. 1486896