RU2096770C1 - Method determining thermophysical characteristics of materials and device for its implementation - Google Patents

Abstract

FIELD: measurement technology, thermal physical, chemical, construction and other fields of economy to test quality of articles under laboratory and field conditions of usage. SUBSTANCE: method determining thermophysical characteristics of materials lies in action with thermal pulses of constant power and repetition rate on surface of tested object. Rate of change of temperature at moment of feed of paired (n-I)-th, n-th and (2n-I)-th, 2n-th pulses is recorded at point located at fixed distance from line of thermal action. Sought-for characteristics are calculated by it. Device for implementation of method has programmable microcalculator 12, permanent storage 11, on-line storage 6, multiplexer 8, unit 7 of time intervals, pulse feed unit 5, measurement probe 1, D.C. amplifier 2, analog-pulse converter 3, synchronization unit 9, address counter 10 and pulse counter 4. EFFECT: enhanced authenticity of method and reliability of device. 2 cl, 1 dwg

Description

 The present invention relates to the field of thermophysical measurements, in particular to the determination of the thermophysical characteristics of materials, and can be used in chemical, construction and other areas of the national economy to control the quality of products in laboratory and field conditions.

A device for determining thermophysical characteristics (A.S. N 1236355 USSR, class G 01 N 25/18, B.I. N 21, 1986), which contains a thermal probe in the form of a material with known thermophysical characteristics, on the contact surface probe mounted linear wire heater and two thermocouples at a distance x ₁ and x ₂ from the line of action of the heater, the third thermocouple located inside the material of the thermal probe at a distance x from the line heater ₃ steps, analog-to-digital converter, a power supply unit, microprocessor unit centuries O yes, controlled frequency dividers, frequency divider and 2I-NOT element.

The method of monitoring the thermophysical characteristics (a.c.SSSR N 1236355) in this device includes pulsed heating of the heat-stabilized surfaces of the reference and test samples, consisting of measuring temperature at a distance of x ₁ and x ₂ from the line of action of the heater, and at the third point x ₃ located inside the reference material. After a specified period of time, temperatures are fixed at these points. The desired characteristics are calculated according to the given formulas.

 The disadvantage of this device and method is the use of three measurement channels, which leads to hardware complications and reduced measurement accuracy, as well as expanding the measurement range to the calculation of parameters by the iteration method in an implicit form.

 The prototype adopted a method of monitoring the thermophysical characteristics of insulating materials (A.S. N 1711052 (CCCP), CL G 01 N 25/18. Bull. N 5, 1992), including pulsed heating of thermostated surfaces of the samples by a source according to a linear law, measuring intervals time from the moment the first impulse is applied to the moment the samples reach the set temperature at points located at a fixed distance from the heating point.

 The measured time intervals are determined in the process of comparing the set and recorded temperatures, which require mandatory temperature control of the samples to a steady state, taken as a reference point for temperature. In this case, the experiment is divided into two stages: thermal stabilization and measurement. Moreover, most of the time is spent on thermal stabilization, especially during a series of experiments. The thermal stabilization error affects the experimental results and reduces the accuracy of the determination of TFC by this method.

 The device, taken as a prototype (AS N 1298713 (USSR), class G 05 B 19/18, 1987, Bull. N 11), consists of a multiplexer, programmable microcalculator, pulse generator, read-only memory, memory interface , analog-to-digital converter, DC amplifier, stabilized voltage unit, measuring probe and actuator unit.

 The disadvantages of this device are the low information content due to the input / output of information through a standard interface, low performance in the measurement and management of information, as well as the limited flexibility of the architecture. The standard interface 145IK1801 for one machine cycle of the microcalculator inputs or outputs one bit of information, and the message exchange is provided with a limited area of the register memory of the number-pulse microprocessor of the programmed microcalculator.

 The aim of the invention is to increase metrological characteristics, namely: accuracy, information content and speed.

This goal is achieved by the fact that in
1. a method for determining the thermophysical characteristics of materials, which consists in the fact that the surface of the test object is exposed to a line with constant-output heat pulses and a repetition period, the temperatures are recorded at a sample point located at a fixed distance from the exposure line, unlike the prototype, temperature measurements are carried out at the moment of supplying paired (n -) th, n-th and (2n-1) -th, 2n-th pulses, the temperature changes are recorded, according to which the desired characteristics are calculated.

 2. a device for determining the thermophysical characteristics of materials containing a programmable microcalculator, a time interval block, a switching power supply, a measuring probe, a DC amplifier, an analog-pulse converter, a pulse counter and a multiplexer, the second information inputs of the latter are connected to the corresponding outputs constantly memory device, in contrast to the known solutions, additionally introduced operational memory, synchronization unit and an address counter, the clock input of which is connected to the corresponding output of the programmable calculator, and the installation input through the synchronization unit is connected to the information input of the RAM, multiplexer and the output of the information line of the latter combined with the output of the multiplexer, the address inputs of which are bitwise connected to the output of the address counter , the same inputs of the permanent storage device, a block of time intervals and random access memory, connect nnogo information output through the block of time slots to the second address inputs of the multiplexer and the clock inputs of the pulse counter.

где: a, λ соответственно температуро- и теплопроводность материала, X - расстояние между линией нагрева и точкой контроля на поверхности материала.The essence of the method is as follows. On the test material, heat pulses are supplied with a constant power q and with a constant period of 7t _{o The} temperature values are recorded at the ith moments of the supply of the (n-1) th, n-th, 2n-th and (2n-1) -th pulses . The temperature T _p after supply p = 2n, where n = 2, 3. thermal pulses is expressed by the dependence:

where: a, λ, respectively, the thermal and thermal conductivity of the material, X is the distance between the heating line and the control point on the surface of the material.

Соответственно

Откуда находим систему уравнений:

Поделив V_k на V_i, получим:

После несложных преобразований имеем:

Если принять, что k=2i, тогда:

Предложенный способ реализован устройством, структурная схема которого приведена на фиг. 1. Устройство состоит из измерительного зонда (ИЗ) 1, усилителя постоянного тока (УПТ) 2, аналого-импульсного преобразователя (АИП) 3, счетчика импульсов (СИ) 4, импульсного блока питания (ИБП) 5, оперативно-запоминающего устройства (ОЗУ) 6, блока временных интервалов (БВИ) 7, мультиплексора (М) 8, блока синхронизации (БС) 9, счетчика адресов (СА) 10, постоянно-запоминающего устройства (ПЗУ) 11 и программируемого микрокалькулятора МК-61 (ПМК) 12.Their rate of change of V _k , V _i temperatures at the k-th and i-th step is written as:

Respectively

Where do we find the system of equations:

Dividing V _k by V _i , we get:

After simple transformations, we have:

If we assume that k = 2i, then:

The proposed method is implemented by a device whose structural diagram is shown in FIG. 1. The device consists of a measuring probe (IZ) 1, a direct current amplifier (UPT) 2, an analog-pulse converter (AIP) 3, a pulse counter (SI) 4, a pulse power supply (UPS) 5, random access memory (RAM) ) 6, a block of time intervals (BVI) 7, a multiplexer (M) 8, a synchronization block (BS) 9, an address counter (CA) 10, a read-only memory device (ROM) 11 and a programmable microcalculator MK-61 (PMK) 12.

 FM1 converts the temperature from a linear heater into an electrical signal.

 UPT2 amplifies the constant voltage removed from the measuring cell to the required level.

 AIP3 converts the input voltage coming from UPT2 into pulses, the frequency of which linearly depends on the voltage value.

SI4 converts the frequency measurement signal F _meas. into the code.

 UPS5 is required to power the entire circuit and generate heat pulses for the measuring probe.

 RAM6 is intended for temporary storage of control information.

 BVI7 generates control signals of UPS5, SI4, M8, respectively, at outputs 16, 17, 18.

 M8 converts parallel information from ROM11, SI4, BVI7, synchronously to the address of inputs 13 of CA10 into serial and enters PMK12 into the dynamic memory ring.

 BS9 synchronizes the operation of CA10 with the dynamic memory PMK12.

 CA10 generates an address code corresponding to the temporary information address in the dynamic memory ring PMK12.

 ROM11 is necessary for storing work programs.

 PMK2 serves to process the measured information, calculate the thermophysical characteristics, adjust the results to a reference value, and output the results.

 The device operates as follows. At the initial time, the dynamic memory ring PMK12 is closed.

 At the output of BS9, pulses are formed that determine the conditional start of the machine cycle. The pulses act on the installation input CA10 and write to it a zero address, which is synchronized with the beginning of the machine cycle. The movement of information along the highway occurs synchronously with the frequency that arrives at the clock input CA10 from the corresponding output PMK12. The appearance of each bit of information on the PM0k12 trunk corresponds to a certain code on the address bus CA10. It is a parallel address of the familiarity of information passing through the PMK12 dynamic memory ring.

 In the mode of entering the program into the memory of PMK12, the information is written to RAM 6 from the corresponding output of PMK12 via the information highway, the code from which is fed to the BVI 7 through the information outputs, generating control signals at the second address inputs 14 of the multiplexer 8, through which the outputs 15 of the ROM 11 are switched with the information highway PMK 12. The address inputs of the ROM 11 receive the codes from the counter CA 10 at the address outputs. In the dynamic memory ring PMK 12, information is replaced, the dynamic memory ring is closed again. Thus, direct access to the dynamic memory of the PMC 12, which has the maximum speed.

 In the mode of outputting information from the PMK 12 through the information highway to RAM 6, data is received, the address inputs of which are scanned by CA 10. The recording time is equal to the duration of the machine cycle, at the end of which the PMK 12 stops sending signals through the information highway.

 The measurement mode includes the input of information from SI 4 and differs from the input mode of information from RAM 6 in that it is recorded in one memory register PMK 12. At the same time, from BVI 7 to the second address inputs 14 of multiplexer 8, the control signal arrives at the moment of passage through information highway information of this register.

 The conversion of the frequency from the AIP 3 to the code is carried out using SI 4 for a fixed time interval. Pulse counting is performed by a SI 4 hardware-binary binary decimal counter. BVI 7 sequentially generates the following control signals at the clock outputs 17 for SI 4: zeroing; Decrease account resolution prohibition of account; resolution of the invoice for increase; prohibition of the account (storage of the code for recording in PMK 12). The counting of impulses to decrease is made without a signal at the input of UPT 2, and the counting to increase with an attached sensor. Thus, in the converted signal eliminates the temperature drift UPT 2.

Proof of effectiveness
1) By efficiency.

 a) measurements.

где τЭ₁ и τЭ₂ -время проведения эксперимента предлагаемым способом и прототипом соответственно

где τt₁,τt_2/ время термостатирования для предлагаемого способа и прототипа соответственно,
τЭ₁,τЭ₂ время измерения для предлагаемого способа и прототипа соответственно,
т. к. τu₁= τu₂= τu, тогда

что видно из условия определения относительной погрешности e измерения температуры

Тогда эффективность будет иметь вид:

Например, для

Т. е. оперативность предлагаемого способа в

раз выше, чем у прототипа.The effectiveness of the proposed method is determined by the ratio

where τE ₁ and τE _{2 are the} time of the experiment by the proposed method and prototype, respectively

where τt ₁ , τt _{2 /} temperature control for the proposed method and prototype, respectively,
τE ₁ , τE ₂ measurement time for the proposed method and prototype, respectively,
since τu ₁ = τu ₂ = τu, then

as can be seen from the conditions for determining the relative error e of temperature measurement

Then the efficiency will look like:

For example, for

That is, the efficiency of the proposed method in

times higher than that of the prototype.

 b) experiment.

 Efficiency will be determined by attitude.

время измерения прототипа и предлагаемой системы соответственно.

the measurement time of the prototype and the proposed system, respectively.

τ ₁ = τu ₁ + τv ₁ + τp ₁ ,
where τu ₁ is the measurement time,
τv ₁ - input time,
τp ₁ is the calculation time of the program.

τu ₁ ≃ τv ₁ ≃ τp ₁ = τ = 0.1 (s) ..

Откуда

Следовательно, быстродействие прототипа в 4 раза ниже, чем у предлагаемой системы.Therefore, τ ₁ ≃ 4τ

Where from

Therefore, the speed of the prototype is 4 times lower than that of the proposed system.

 2) For informational content.

где t - время ввода информации,
N объем вводимой информации в число-импульсном коде.Information content is determined by the formula:

where t is the time of information input,
N is the amount of input information in a pulse number code.

где I₁ информативность прототипа, которая определяется по формуле (1),
I₂ информативность предлагаемой системы, которая определяется по формуле (2).Then the effectiveness of the proposed system will be determined by the ratio

where I _{1 the} information content of the prototype, which is determined by the formula (1),
I _{2 the} information content of the proposed system, which is determined by the formula (2).

где N₁=4 бит. τ₁0,1 (сек).

where N ₁ = 4 bits. τ ₁ 0.1 (s).

где N₁=2•n•m, где n=4 бит. m=12, число регистров, τ₂0,02 (сек).

where N ₁ = 2 • n • m, where n = 4 bits. m = 12, the number of registers, τ ₂ 0,02 (sec).

получим:

Следовательно, информативность предлагаемой системы в 120 раз больше, чем у прототипа.Expressing τ ₁ in terms of

we get:

Therefore, the information content of the proposed system is 120 times greater than that of the prototype.

 3) In terms of flexibility.

где Г₁ и Г_2> гибкость прототипа и предлагаемой системы соответственно,
Г₁=N₁ позиционный код,
Г₂=N₂ двоичный код.Efficiency is determined by the ratio

where G ₁ and G _{2> the} flexibility of the prototype and the proposed system, respectively,
G ₁ = N ₁ position code,
G ₂ = N ₂ binary code.

Откуда

Следовательно, гибкость предлагаемой системы в 256 раз выше, чем у прототипа.

Where from

Therefore, the flexibility of the proposed system is 256 times higher than that of the prototype.

по оперативности эксперимента в 4 раза, по информативности в 120 раз, по быстродействию в 256 раз.That is, the effectiveness of the proposed system increases in the efficiency of measurement in

by the efficiency of the experiment by 4 times, by the information content by 120 times, by the speed by 256 times.

 The proposed method and device are implemented in the measuring and computing system TEMP-073, made at the PMK "Electronics MK-61", microcircuits of the K564, K140, K142, K168 and K573 RF2 series, the measuring probe contains a housing, a cartridge holder, a spring and a reference cartridge material on which two pairs of thermoelectric converters of calibration of ХК are fixed with a diameter of 0.1 mm, and also a heater from nichrome with a diameter of 0.1 mm.

, а эксперимента в 4 раза, соответственно информативности в 120 раз, а гибкости -в 256 раз.Thus, recording the speed of temperature changes between paired pulses in the method and introducing into the device a synchronization unit and an address counter for organizing direct access to the PMK12 information highway allow, in contrast to known technical solutions, to increase the measurement efficiency in

, and experiment 4 times, respectively, information content 120 times, and flexibility 256 times.

Claims (2)

 1. The method of determining the thermophysical characteristics of materials, which consists in the fact that the surface of the test sample is exposed in a line to the heat pulses of constant power and the repetition period, temperature is recorded at a point located at a fixed distance from the line of action on the surface of the sample, characterized in that the temperature and the rate of its change is recorded at the moments of supply of paired (n-1) -th, n-th and (2n-1) -th, 2n-th pulses, and the desired characteristics are calculated from the measured values, where n is 2.3.  2. A device for determining the thermophysical characteristics of materials, containing a programmable microcalculator, a time interval unit, a switching power supply, a measuring probe, a DC amplifier, an analog-pulse converter, a pulse counter and a multiplexer, the second information inputs of the latter are connected to the corresponding outputs of the permanent memory device, characterized in that the additionally introduced random-access memory, synchronization unit and an address meter whose clock input is connected to the corresponding output of the programmable calculator, and the installation input through the synchronization unit is connected to the information input of the random access memory device, the corresponding third input of the multiplexer and the output of the information line of the programmable calculator, the input of the information line of the latter is combined with the output of the multiplexer, address inputs which is bitwise connected to the outputs of the address counter, the inputs of the same name are constantly memorized separating apparatus, the block of time slots and operational storage device connected through the output unit information of time slots to the second address inputs of the multiplexer and the clock inputs of the pulse counter.