JPS6059540B2 - Thermal conductivity measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring thermal conductivity called the so-called unsteady hot wire method, and an apparatus for automatically measuring thermal conductivity based on this method.

To explain the conventional unsteady hot wire method in detail, for example, a heating wire is placed on the central axis of a cylindrical sample, a constant electric power is supplied to each heating wire, and the temperature change at the heating wire or near the heating wire is measured. is measured by a temperature measuring element, and the thermal conductivity of the sample is calculated based on this temperature change.

That is, when power is supplied to the heating wire, heat is generated from the heating wire, and this heat diffuses within the sample and escapes to the outside. Therefore, if the thermal conductivity of the sample is high, the heat generated by the heating wire will be easily diffused and the temperature of the heating wire will rise slowly, but if the thermal conductivity of the sample is low, the heat generated by the heating wire will be diffused easily. It is difficult to diffuse, so the temperature of the heating wire rises at a steep gradient. (Note that this phenomenon applies immediately after the start of power supply, but is a phenomenon observed after a certain period of time has elapsed from the start of power supply, as will be described later). Focusing on such a phenomenon, thermal conductivity can be measured by measuring the temperature change of the heating wire. Next, the above phenomenon will be explained theoretically.

The heat diffusion equation is generally expressed by the following equation. here T: temperature τ: time α: Thermal diffusivity r: Distance from heat source (heating wire) When solving equation (1) above, the following three conditions are substituted.

The first condition is the second condition is The third condition is - Here q is the heat flow from the heating wire It can be expressed as

However, R: resistance of the heating wire 1: current flowing through the heating wire L: length of the heating wire When equation (1) is solved considering the above three conditions, EI represents the integral index function, λ: heat of the sample Conductivity γ: Euler's constant (=0.5772...ri above (2
), if -1- is sufficiently small, then
The higher-order terms after 4αγ−C1 can be ignored and are expressed by the following equation, 4ατ.

Here, the time τ is the limit 4ατ for which the assumption that -1- is sufficiently small holds true.

'', equation (3) holds true on the condition that τ≧γo''. In the conventional thermal conductivity measurement method, the above-mentioned time τ. Temperature Tl at two points in time τ1 and γ2 after ``
Thermal conductivity is determined by measuring T2. To explain in detail, if we substitute the measured temperature T1 at time τ1 into equation (3), and set the temperature measured at time τ2 as T2, we get (3)
Substituting the expression (5)-(4) as a substitute, the following holds true.

As is clear from equation (6), the thermal conductivity λ is τ1,
It is determined by measuring the temperature Tl, T2 of the heating wire or the vicinity of the heating wire at time τ2. However, the conventional method described above has the following disadvantages.

In other words, errors within a certain range are unavoidable in the measured values, and as described above, the heating wire temperatures at time τ1 and time τ2 are measured, and the measured temperatures Tl and T2 are substituted into equation (6) to calculate the temperature. When determining the conductivity, the errors in the measured temperatures Tl and T2 directly affected the thermal conductivity value, making it difficult to accurately measure the thermal conductivity. In particular, when calculating the thermal conductivity by automatically measuring the measured temperatures Tl and T2 with a thermal conductivity measuring device, it is difficult to correct the error in the measured temperature, and it is difficult to accurately measure the thermal conductivity. It was not possible to measure it.
In addition, in the case of samples with particularly high thermal conductivity, thermocouples (
The output from the thermometer (temperature measuring element) was small, and therefore measurement errors had a large effect on thermal conductivity, making it even more difficult to accurately measure thermal conductivity. This invention was made based on the above-mentioned circumstances, and its purpose is to:
By measuring thermal conductivity based on the integral value of measured temperature over time, we provide a method to accurately measure thermal conductivity without being affected by measurement errors due to specific points in time, and we also implement this measurement method. There is an attempt to provide a device that can automatically measure thermal conductivity.

Next, we will discuss the theory underlying the present invention.

When the above-mentioned equation (3) is integrated over time τ1 to τ2, the following is obtained. In equation (7), the second term on the right side is moved to the left side, and both sides are τ2−γ1 (γ2〉τ1
), the following formula is obtained.

Similarly, equation (3) can be expressed as time τ3~τ, (where τ4〉τ3
, τ1 × τ4), the following equation is obtained.

Then, the following equation is obtained by calculating equation (9)-(8).

When calculating the thermal conductivity from this equation, this equation (11) is a general equation for calculating the thermal conductivity λ by the method of the present invention.

Therefore, in the method of the present invention, τ1, τ2, τ
3, τ, and set the time τ1 to τ2 and the time τ3 to τ
, the integral value fτ, Tdτ of the measured temperature T of the heating wire for ,
Thermal conductivity λ can be determined by determining and fτJdT and substituting this into equation (11).

In this way, the integral values of the measured temperature fτJdτ, FTJdτ
Since there is a method for determining λ based on the temperature, it is possible to prevent an error in the measured temperature at a specific point from directly affecting the value of the thermal conductivity λ, and it is possible to determine the accurate thermal conductivity λ. In addition,
If we add the condition τ2-τ1=τ4-τ3, we get (11
) formula can be simplified as follows.

Furthermore, if we add the condition τ2=T3=γ9, (12
) can be further simplified as follows. The method for measuring thermal conductivity described above is applied when the entire sample is made of a material with unknown thermal conductivity, but in the present invention, the sample is divided in half and one half is made of a material with unknown thermal conductivity. It can also be applied to the case where the thermal conductivity is measured by forming one of the two materials, the other being formed of a material with known thermal conductivity, and interposing a heating wire and a temperature measuring element between the two. In this case, in the conventional measurement method, the thermal conductivity λ of the unknown sample is determined by calculating the following equation. However, H is a value corresponding to the thermal conductivity of a known sample, and K is a constant.

According to the present invention, the integral form of equation (14) is obtained by the following equation.

Here, the constants K'' and H'' can be determined using a separately prepared standard sample with a fixed thermal conductivity, and τ1 to τ4 are also constants that can be determined in advance.

Therefore, the thermal conductivity λ can be determined based on the value of f:1Tdτ−f Tdτ. First, the probe section 1 used in the method of the present invention will be explained with reference to FIG.
That is, the sample 2 whose thermal conductivity is to be measured consists of, for example, semi-cylindrical sample structures 2a, 2a, which are polymerized to form a columnar shape. Further, the heating wire 3 is sandwiched between the sample constructs 2a, 2a, and is arranged at the central axis of the sample 2 when these are polymerized. This heating wire 3 is made of a round wire, a band wire, or the like. A temperature measuring element such as a thermocouple 4 is placed in the center of the heating wire 3.
A hot contact 4a is attached by spot welding or the like. 5 in the figure is a U-shaped support frame, and the heating wire 3 is connected to the terminals 6, 6 at the ends of the support frame 5.
is fixed at both ends so that it remains straight. Further, both ends of the thermocouple 4 are connected to other terminals 7, 7 at the ends of the support frame 5. Note that the thermal contact point 4a may be placed near the heating wire 3. Next, a case in which the method of the present invention is implemented based on recording by a pen recorder will be explained with reference to FIG.

That is, the output v of the thermocouple 4 after starting the supply of constant electric power to the heating wire 3 is recorded by a pen recorder (not shown). As a result, the curve shown in FIG. 2 is drawn on the recording paper. Then, portion A and portion B of this recording paper are cut out, and their weights are measured separately using a precision scale.
Assuming that the weights of portions A and B are MA and mB is, for example, Mg, the following equation holds true. Similarly, here, Vc: for easy measurement and calculation.
Cut voltage ρ: Weight per unit area of recording paper (
Unit: Tn9/MiL) a: Area of recording paper corresponding to 1 mV, 1 second square (Tnlt
/MV-S) i: Average thermoelectric power (° C./MV) In addition, Vc in FIG. 2 is a pre-cut voltage.

Here, the average thermopower i is the measured temperature at τ1 and γ4.
When T1+T4 degrees are Tl and T4, it is determined as the thermoelectric power corresponding to the temperature.

Then, these f: (3Tdτ, f13Tdτ are (1
The thermal conductivity λ is determined by substituting the third wiping. Next, the case where the method of the present invention is implemented using a digital printer will be explained with reference to FIG. In other words, the output V of the thermocouple 4 (it may be pre-cut using the output VO at the zero point)
is drawn using a digital printer as shown in Figure 3. To be more specific, the integral value of the temperature T of the heating wire 3 for τ1 to τ23 and the integral value for τ3-τ4 are determined by using, for example, a voltage value every second as a proxy, as follows.
In this example, τ1 = 30 seconds, τ = 45 seconds, τ, = 6
Calculate as @. Here, ■30...V6O is the output voltage at each time point 3...6.

Thermal conductivity λ is determined by substituting these f:I3Tdτ and f;1Tdτ into equation (13).

Next, an apparatus for implementing the method of the present invention and automatically measuring thermal conductivity by digital calculation will be described with reference to FIG.

Reference numeral 1 in FIG. 4 is the probe section whose details are shown in FIG. and is supplied to the first input terminal 14a of the analog multiplexer 14. On the other hand, the temperature of the cold junction of the thermocouple 4 is measured by an automatic cold junction compensator 15 that includes, for example, a resistance temperature detector, and the output of this compensator 15 is amplified by a cold junction amplifier 16 and then measured. , is supplied to the second input terminal 14b of the analog multiplexer 14. A first input 14 of these analog multiplexers 14
The outputs supplied to a and the second input terminal 14b serve as information for calculating the temperature to be measured Tm, as will be described later. The output of the thermocouple 4 is amplified by the preamplifier 12 and subtracted by the precut level by the precut circuit 17, and then supplied to the integrator 42, and the output integrated by the integrator 42 is the analog The signal is supplied to a third input terminal 14c of the multiplexer 14. The output supplied to the third input terminal 14c becomes information for calculating the thermal conductivity as described later. And this analog multiplexer 1
Each analog data supplied to the analog multiplexer 14 is sent to the A/D converter 18 and converted into digital data according to the control signal output to the control input terminal of the analog multiplexer 14, and is further converted to digital data by the digital input circuit 19, Via the processing device 20. and stored in the storage device 21. Note that a reset signal and a start signal are input to the dump circuit 19 through a reset button 22 and a start button 23.

The processing device 20 also includes a digital out circuit 24, D
/． A precut voltage signal is output to the precut circuit 17 via the A converter 25. Furthermore, the processing device 20 is connected to the integrator 42 via the digital out circuit 24.
It is designed to output an integration start signal. Further, the processing device 20 is configured to control a thermal conductivity digital display device 26, a temperature to be measured digital display device 27, and a ready 0K lamp 28 via a digital Luout circuit 24. The details will be described later. Further, the output of the thermocouple 4 described above is outputted to a recorder 30 and a moving coil indicator 31 via a preamplifier 12 and another pre-cut circuit 29. These recorder 30 and moving coil indicator 31 are designed to constantly display the heating wire temperature in analog form. Further, the circuit can be calibrated by switching the mode switch 11 mentioned above to connect the circuit to the internal reference voltage generator 32. Further, a signal is outputted from the mode switch 11 to the digital input circuit 19 to inform whether the mode is in measurement mode or calibration mode. Next, a circuit for power supply control will be explained. That is, the input of the alternating current voltage (AClOOV) is supplied to the power supply circuit 35 via the power switch 33 and the fuse 34. This power supply circuit 35 rectifies and transforms the input AC voltage (AClOOV), and supplies a DC voltage of 5 to 15 V to the power supply circuit 41 for the control circuit described above.

Further, this power supply circuit 35 is configured to supply constant power to the heating wire 3 via a DC constant current circuit 36 and a current controller 37. Note that 38 is an ammeter that constantly displays the current flowing through the heating wire 3 in analog form. Reference numeral 39 denotes a current value switch, and when current value information is supplied to the current controller 37, it is supplied to the storage device 21 via the digital input circuit 19 and the processing device 20. Further, the start signal from the start button 23 described above is sent to the processing device 20.
, is outputted to the current value controller 37 via the digital out circuit 24, and thereby the power supply to the heating wire 3 is started. Next, the operation of the measuring device having the above-mentioned configuration will be explained.

As an example, a case where the temperature to be measured is higher than room temperature will be described. First, the sample 2 is placed in a heating furnace (not shown) and heated. After a suitable period of time has elapsed after the start of heating and a stable state is reached, the power switch 33 is turned ON and the reset button 22 is pressed to clear the memory device 21. Thereby, measurement of the heating wire temperature is started. That is, the output of the thermocouple 4 is outputted to the analog multiplexer 14 via the temperature measurement amplifier 13, and further to the A/D converter 18.
After being converted into a digital signal, it is sent to a storage device 21 via a digital input circuit 19 and a processing device 20. This temperature information is sent out at predetermined time intervals by a control signal sent to the analog multiplexer 14. Note that the ready 0K lamp 28 always lights up after a certain period of time has passed after the start button 23 is pressed. After confirming this lighting, the operator presses the start button 23. Then,
A start signal is supplied to the processing device 20 via the digital input circuit 19. Further, this start signal is outputted from the processing device 20 via the digital out circuit 24 to the current value controller 37, and the current value controller 37 starts supplying constant power to the heating wire 3 upon receiving this signal. Note that this time point at which power supply starts is referred to as the zero time point. Then, the processing device 20 that receives the output information (1) of the thermocouple 4 when τ1 hours have passed from this zero point transmits the information V1 to the D/A converter 25.
Upon receiving this, the D/A converter 25 supplies analog information V1 to the pre-cut circuit 17.

Therefore, at time τ1, the output sent from the thermocouple 4 to the pre-cut circuit 17 is reduced by the output from the D/A converter 25, and thus the pre-cut circuit 17
The output to the integrator 42 becomes 0V at this time point τ1. After the processing device 20 detects that the output to the integrator 42 is O■, an integration start signal is output from the processing device 20 to the integrator 42 via the digital out circuit 24, and the The integrator 42 then starts an integration operation. Note that the output of the pre-cut signal, the integrator 4
Since the confirmation of the 0V output to 2 is done in a very short time, it is safe to assume that the integrator 42 starts its integration operation at time τ1. Furthermore, at the time τ, the processing device 20 outputs a control signal to the a9log multiplexer 14, which causes the integral value f:I3 of the output of the pre-cut thermocouple 4 from the time τ1 to the time τ3.
Vdτ This corresponds to the information of the integral value f:RTdτ when the temperature of the heating wire 3 is T, as will be described later. ) is converted into digital information by the A/D converter 18 and stored in the storage device 21 via the digital input circuit 19 and the processing device 20. Further τ
At time point 4, a control signal is output from the processing device 20 to the analog multiplexer 14, and as a result, integral value information f: 1Vd from τ1 to τ4 is output in the same manner as described above.
τ is stored in the storage device 21. Then, the processing device 20 performs the following calculation based on the information f:IVdτ and FTTlVdτ stored in the storage device 21. That is,
Subtract the above information to obtain the following value. This x is equivalent to FIC3■dγ-f:I3■dτ from the following equation.

That is, the value Fg3Tdτ-f:I3Tdτ at 13 wipes described above has the following relationship with the value f:13Vdτ-f:I3Vdτ obtained by equation (21).

However, i is the average thermoelectric power.

Therefore, the processing device 20 calculates equation (13) by performing the following division, and can determine the thermal conductivity λ.

here is a constant stored in the storage device 21 in advance.

Information on the current value 1 is supplied from the current value switch 39 to the storage device 21 via the digital input circuit 19 and the processing device 20, and is the resistance R per unit length of the heating wire 3. , thermoelectric power completion, time γ1, τ23, and τ4 are also supplied in advance to the memory circuit 21 via the processing device 20.
Information on the thermal conductivity λ calculated in this way is sent to the thermal conductivity digital display device 2 via the digital out circuit 24.
6 and displayed here. In addition, the temperature to be measured Tm
is calculated from the temperature information TO, T4 stored in the storage device 21 by the following equation in the processing device 20. Note that these temperature information T.

, T4 are the first and second
It is determined by the calculation of the processing device 20 based on the data output to the input terminals 14a and 14b. Further, the temperature to be measured Tm is digitally displayed on the temperature to be measured display device 27 under the control of the processing device 20. Next, an apparatus for implementing the method of the present invention and automatically measuring thermal conductivity by analog calculation will be explained based on FIG.

That is, 1 in FIG. 5 indicates the probe section detailed in FIG. 1, and the heating wire 3 is connected to a DC constant current power source 51 via a current controller 50. On the other hand, the output of the thermocouple 4 is amplified by the preamplifier 52 and becomes information for calculating the temperature to be measured, as well as information for calculating the thermal conductivity. First, the case where the information is used as information on the temperature to be measured will be described. The output from the preamplifier 52 is sent to a storage circuit 55 via a cold junction compensation circuit 53 and an adjustment amplifier 54. This memory circuit 55 is constructed by connecting in parallel a circuit of a memory M1 consisting of a relay R1 as a switching means and a capacitor, and a circuit of a relay R2 and a memory M2 as a switching means. And each memory Ml, M2
The analog information stored in is added by an adder 56 to calculate the temperature to be measured Tm, and this calculation result is sent to a temperature to be measured display device 57. In addition,
The detailed operation will be described later. Also, to explain the case where the output from the thermocouple 4 is used for thermal conductivity calculation, this output is sent to a pre-cut circuit 58, and from this pre-cut circuit 58 is sent to the inverting input terminal of a subtracter 59. and relay R3 as a switching means.
It is designed to be sent to the non-inverting input terminal via.

A memory M3 is connected to the relay R3. The output of this subtracter 59 is integrated by an integrator 60 and then sent to a memory circuit 61. This memory circuit 61 includes a circuit consisting of a relay R4 as a switching means and a memory M. It is constructed by connecting a circuit consisting of a relay R as a switching means and a memory M5 in parallel. And these memories M
4. The information stored in the memory M5 is sent to each input terminal of the subtracter 62. The output of this subtracter 62 is sent to an arithmetic unit 63. Further, the output of the thermocouple 4 is sent to a compensation circuit 64 via a preamplifier 52 and a precut circuit 58. The compensation circuit 64 calculates compensation coefficient information, which will be described later, based on this analog information and outputs it to the arithmetic unit 63. In the arithmetic unit 63, a memory circuit 61, a compensation circuit 6
The thermal conductivity λ is calculated based on the information of 4, and the result is sent to the thermal conductivity display device 65. In addition, 66 is a control circuit, and this control circuit 66 receives the pulse signal from the pulse generation circuit 67, and the DC constant current power supply 5
1. Control signals are output to relays R1 to R. Next, the operation of the device having the above configuration will be explained.

As an example, a case where the temperature to be measured is higher than room temperature will be explained. When the temperature of the sample 2 placed in the heating furnace becomes constant near the temperature to be measured Tm, the precut voltage in the precut circuit 58 is set by the volume 58a of the precut circuit 58 so that it becomes the same value as the output voltage from the thermocouple. do. As a result, the output voltage from the pre-cut circuit 58 at this point becomes zero. Next, a start signal is sent to the control circuit 66, and upon receiving the start signal, the control circuit 66 outputs a power supply start signal to the DC constant current power source 51, thereby starting the supply of constant power to the heating wire 3. and,
The control circuit 66 sends a control signal to the relay R1 at the start of power supply (zero time) to switch the relay R1 from ON to OFF. As a result, temperature information T at the zero point is output from the thermocouple 4. The voltage corresponding to memory M1
is stored in Further, the control circuit 66 sends a control signal to relay R2 at time τ, turning this relay R2 to 0N.
This causes memory M2 to have τ
A voltage corresponding to temperature information T4 at four points in time is stored. The temperature information T stored in these memories M, , M2. , T, are sent to an adder 56, where the temperature to be measured Tm is calculated. The measured temperature Tm calculated by this calculation is measured by the measured temperature display device 57.
sent to and displayed here.

In this display device 57, the analog information output from the adder 56 may be displayed in analog form as it is, or may be converted into digital information by an A/D converter and then displayed digitally. Next, calculation and display of thermal conductivity λ will be explained.

After the above-mentioned zero point, the output from the thermocouple 4 is sent to a subtracter 59 via a preamplifier 52 and a precut circuit 58.

Before time τ1, relay R3 is in the 0N state and the same level of voltage is input to each input terminal of the subtracter 59, so
The output from this subtracter 59 is zero. Therefore, the integrator 60 does not substantially perform an integrating operation. Then, at the time τ1, a control signal is output from the control circuit 66 to the relay R3, and this relay R is switched from 0N to 0FF, so that the output voltage of the thermocouple 4 at the time τ1 is stored in the memory M3. The voltage stored in this memory pigeon is input to the inverting input terminal of the subtracter 59. On the other hand, the output of the thermocouple 4 after time τ1 is input to the non-inverting input terminal of this subtracter 59. As a result, the output from the subtracter 59 after the time τ1 becomes the output from the thermocouple 4 after the time τ1 minus the output at the time τ1, and is output to the integrator 60. Therefore, the integrator 60 substantially starts the integration operation at time τ1 and sends the integration information to the storage circuit 61. and,
The relay R4 in the memory circuit 61 is switched from 0FF to ON at the time τ1 by the control signal from the control circuit 66, and is turned off at the time τ23, so that the memory stores the memory τ1.
The integrated voltage fτ23Vdτ at ~τ23 is stored. Also,
Relay R5 is switched from OFF to ON at time τ1 by a control signal from control circuit 66, and turned OFF at time τ4.
As a result, the memory M, has an integrated voltage fτ from τ1 to τ4,
■Save dτ. The information stored in these memories M4 and M5 is output to a subtracter 62, and the following calculation is performed in this subtracter 62. Here, we have essentially calculated .

This information x is then sent to the arithmetic unit 63.

On the other hand, the compensation circuit 64 outputs information of -48".
η0R0 is done.

The thermal conductivity λ is calculated by this calculator 63, which will be explained in detail below.

That is, as mentioned above, the thermal conductivity λ is determined by (13 times).Since this is here, the following equation is obtained by substituting this for (13 times).

Here, the thermopower η changes slightly depending on the temperature of the thermocouple 4,
The resistance R of the heating wire 3 changes slightly depending on the temperature of the heating wire 3. These changes in η and R are corrected by the compensation circuit 64 described above. That is, in the above equation (24).

However, η. , RO are values at room temperature, for example, 25°C.
Substituting this into equation (23) yields the following equation. Therefore, in the arithmetic unit 63, the preset constant compensation circuit 64
The thermal conductivity λ can be calculated by multiplying the information value from, for example, 1.05 and dividing this by the information X from the subtracter 62.

Note that the information output from the compensation circuit 64! The meter is determined based on information outputted from the thermocouple 4 to the compensation circuit 64 via the preamplifier 52 and the precut circuit 58. The thermal conductivity λ thus calculated by the calculator 63 is output to the thermal conductivity display device 65 and displayed there.

In addition, in this display device 65, the analog information of the thermal conductivity λ may be displayed in analog form as it is, or may be converted into digital information by an A/D converter and displayed digitally. As explained above, according to the method recited in claim 1, the integral value fτJdτ of the temperature of the heating wire or its vicinity between the two time points τ1 and τ2 after the start of power supply to the heating wire, that is, after the zero point, is calculated. , the difference fτ from the integral value FTJdτ (however, γ, <T4) of the measured temperature T between two points τ3, τ
Thermal conductivity is measured based on J(1τ-fτ, TdT).

Since the thermal conductivity λ is determined based on the integral value in this way, it is possible to prevent errors in the measured temperature at a specific point from directly affecting the thermal conductivity value, and to obtain an accurate thermal conductivity λ. be able to. It is particularly effective for materials with high thermal conductivity. Further, according to the thermal conductivity measuring device described in claim 4, the thermal conductivity can be digitally calculated and automatically measured and displayed, and the thermal conductivity as described in claim 5 can be used. The rate measuring device automatically measures and displays thermal conductivity by analog calculation.

Moreover, according to these measuring devices, the integration operation of the integrator is started at time τ1, and the integral value information F7ryoVdτ, fτ4Vdτ is taken out from the integrator at time τ23 and τ4, and based on this integral value information, X=fτ, Vdτ−2fT
dτ (this value X corresponds to the information fτ13Tdτ−fτ, 3Tdτ) is calculated and the thermal conductivity is determined based on this X, so only one integrator is required and the structure is It becomes simple and the calculation accuracy improves.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a probe section used in the method and apparatus for measuring thermal conductivity according to the present invention, FIG. 2 is a diagram illustrating an embodiment of the measuring method according to the present invention, and FIG. Fig. 4 is a block diagram showing an apparatus for automatically measuring thermal conductivity by digital calculation, and Fig. 5 is a block diagram showing a device for automatically measuring thermal conductivity by analog calculation. FIG. 2 is a block diagram showing a measuring device. 2...Sample, 3...Heating wire, 4...
... thermocouple (temperature measuring element), 18 ... A/D converter, 20 ... processing device, 21 ... storage device,
26... Thermal conductivity display device, 42...
Integrator, 60... Integrator, 61... Memory circuit, 62... Subtractor, 63... Arithmetic unit, 6
5... Thermal conductivity display device, 66... Control circuit, R3, R4, R5... Relay (switching means), Ml, N45... Memory.

Claims (1)

[Claims] 1. A heating wire and a temperature measuring element for measuring the temperature of the heating wire or the vicinity of the heating wire are arranged in the sample, and a constant electric power is supplied to the heating wire, and the heating wire or the heating wire is heated. In the method of determining the thermal conductivity of a sample based on nearby temperature changes, two points γ_1 after the start of power supply to the heating wire, that is, the zero point,
The following formula ( 11) A method for measuring thermal conductivity, characterized by calculating the thermal conductivity λ of a sample. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・(11)(
However, q: heat flow from the heating wire) 2 γ_1, γ_2, γ_3, γ_4 are γ_2 - γ_
The method for measuring thermal conductivity according to claim 1, characterized in that 1=γ_4−γ_3. 3 γ_1, γ_2, γ_3, γ_4 are γ_2 - γ_1
The method for measuring thermal conductivity according to claim 1, wherein γ_4-γ_3, and further γ_2 and γ_3 match, so that γ_2=γ_3=γ_2_3. 4. A heating wire placed inside the sample and supplied with constant power, a temperature measuring element also placed inside the sample and measuring the temperature of the heating wire or the vicinity of the heating wire, and the output from this temperature measuring element. an integrator that integrates the voltage V; an A/D converter that converts analog information from the integrator into digital information;
A storage device that stores constants required for thermal conductivity calculation as well as information from the A/D converter, and an integration start signal to the integrator after γ_1 hours have passed from the zero point of power supply start. is output, and the integral value information at γ_2_3 and γ_4 points ∫γ_2_3Vd_γ, ∫γ_4Vd_
γ is stored in the storage device, and these integral value information are subtracted to obtain X=∫γ_4Vd_γ−2∫γ_2_3Vd
Find ＿γ, and from this value X, ∫γ_2_3Tdγ−∫γ_
2_3Tdγ is determined, and based on this value, the following formula (13
1. A digital calculation type thermal conductivity measurement device comprising: a processing device that calculates thermal conductivity λ by calculating ); and a thermal conductivity display device calculated by the processing device. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(13)
(However, q: heat flow from the heating wire, T: temperature) 5. A heating wire placed inside the sample and supplied with constant power, and a heating wire placed inside the sample as well as the above-mentioned heating wire or near the heating wire. A temperature measuring element that measures temperature, an integrator that integrates an output voltage V from the temperature measuring element, a switching means interposed between the temperature measuring element and the integrator, a memory consisting of a capacitor, and a switching device. a memory circuit which stores the output from the integrator, and an intervening circuit between the temperature measuring element and the integrator after γ_1 hours have elapsed from the zero time point of the start of power supply. A control signal is sent to the equipped switching means to start the integration operation of the integrator, and γ_2
At time _3, a control signal is sent to one switching means of the storage circuit to switch this switching means from ON to OFF, thereby storing integral value information ∫γ_2_3Vdγ in one memory, and at time γ_4, the integral value information ∫γ_2_3Vdγ is stored in the other memory circuit. A control circuit that stores integral value information ∫γ_4Vdγ by sending a control signal to the switching means and switching the switching means from ON to OFF, and X=∫ based on the output of each memory of the storage circuit.
A subtracter that subtracts γ_4Vdγ−2∫γ_2_3Vdγ and information X from this subtractor, ∫γ_2_3Td
a calculator that calculates γ−∫γ_2_3Tdγ and calculates the thermal conductivity λ by calculating the following formula (13) based on this value;
An analog calculation-type thermal conductivity measurement device characterized by comprising a thermal conductivity display device that receives an output from the calculation unit and displays thermal conductivity. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(13) (However, q: heat flow from the heating wire, T: temperature)