JPH0692947B2 - Thermal analyzer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal analysis device equipped with a device that corrects the temperature dependence of the detection output of a detection means on the output side.

(Prior Art) For example, in order to analyze the state change of a polymer substance, place a sample container containing a sample and a standard container containing a reference substance on a heat transfer plate arranged in a heating furnace. Measure the differential calorific value detected from the two thermocouples that make up the detection means while heating at a constant rising rate and absorbing and exchanging the heat energy due to the exothermic phenomenon of the sample generated in the process through the heating plate. A heat flux type differential calorimeter is frequently used.

(Problems to be Solved by the Invention) In this type of device, the detection output of the amount of heat absorbed and generated by the sample by the two thermocouples forming the detection means is the heat conduction of the heat transfer plate for exchanging heat energy. It shows that the rate fluctuates as the temperature rises, is affected by heat transfer such as radiation and convection corresponding to the ambient temperature, and decreases as the heating temperature rises. For this reason, the amplitude of the peak waveform indicating the absorption and heat generation of the sample decreases as the heating temperature increases.
Therefore, measures are taken to prevent the heat from escaping from the detection means by covering the lower surface with a glossy uniform heating blog on the heating furnace.Measurement is performed while raising the heating temperature of the heating furnace at a constant rate. As a result, the problem that the amplitude of the output peak waveform fluctuates depending on the temperature cannot be maintained regardless of the change in the ambient temperature.

In view of the above problems, it is an object of the present invention to provide an improved thermal analysis device that corrects the detection output of the detection means so that it is not affected by the ambient temperature on the output side.

(Means for Solving the Problems) That is, the feature of the present invention is that the temperature difference between the reference substance and the sample and the temperature of the sample are separately output, and the amount of heat increases as the temperature of the heating furnace rises. Detecting means having a characteristic that the detection output of the detecting means decreases, and a polygonal function voltage generating means for outputting, as a control voltage, a non-linear voltage that changes in response to an increase in the voltage indicating the temperature of the sample from the detecting means, Having a function of dividing the voltage indicating the temperature difference between the reference substance and the sample output from the means, the control voltage from the polygonal function voltage generating means is input, and the internal resistance corresponding to the amplitude of the control voltage is It is provided with variable resistance means for converting the detection output characteristic of the detection means into a symmetrical characteristic.

(Function) The temperature difference voltage between the reference substance and the sample from the detection means, whose detection sensitivity of the heat quantity decreases as the heating temperature of the heating furnace increases, is input to the variable resistance means, and the sample temperature voltage from the detection means increases. A non-linear voltage whose rate of increase in voltage changes according to the above is input as a control voltage to the control pole of the variable resistance means, and this control voltage causes the internal resistance of the variable resistance means to be symmetrical with the detection output characteristic of the detection means. The temperature difference voltage between the reference material and the sample, which is controlled and corrected so as not to be affected by the detection output of the amount of heat of the detection means, is output.

(Example) Below, the detail of this invention is demonstrated based on the Example shown in a figure.

Each of the drawings shows an apparatus according to an embodiment of the present invention, in which reference numeral 1
Is a thermocouple that supports the sample container 3 in which the sample is inserted and the standard container 4 in which the reference substance is inserted, and detects the sample temperature and the standard substance temperature and outputs the sample temperature and the temperature difference between the reference substance and the sample separately. A heating furnace provided with heat transfer plates 2 made of copper or the like, in which 5, 5'are arranged, and the sensitivity of detecting heat absorption and heat generation of the thermocouples 5, 5'is as shown in FIG. As shown by the characteristic curve a, it has a characteristic of decreasing with an increase in heating temperature. Reference numerals 6 and 7 denote amplifiers for amplifying the temperature difference voltage between the reference substance and the sample detected by the thermocouples 5 and 5 ', and the sample temperature voltage detected by the thermocouple 5', and the amplifier 6 is connected via the resistor R ₀ . Then, as shown by the characteristic curve b in FIG. 2 (B), the FET 12 is connected to the source electrode of the FET 12 which shows the characteristic that the internal resistance rapidly increases in response to the linearly increasing gate voltages O to V _n. 7 is a broken line function voltage generator 8 to 10
Connected with. In the polygonal line function voltage generators 8 to 10, the series circuits of the resistors R _{1 to} R ₃ , R _{4 to} R ₆ , and R _{7 to} R ₉ are connected in parallel, and the feedback loop and the diode D are respectively provided on the output side. Op amps OP ₁ and OP ₂ OP ₃ connected to D, grounding the non-inverting input and having an inverting input terminal are resistors R ₂ and R _{5 respectively.}
And they are arranged in parallel in R _8, further + 15V across branches by applying a voltage different bias voltages of four series-connected resistor circuit sizes applied to a -15V to the inverting input terminal of the operational amplifier OP ₁ to OP ₃ Is configured. As the output voltage of the amplifier 7 increases, the linear function voltage generators 8 to 10 first flow into the resistance circuit in which the above series circuits are connected in parallel, and then the diode D connected to the operational amplifiers OP ₁ , OP ₂ and OP _3. ,
D is sequentially turned on, and a logarithmically compressed polygonal function voltage curve C is output as shown in FIG.
Input to the gate of FET12.

The polygonal line function generators 8 to 9 consider the detection output characteristic of the detection unit and the gate voltage-internal resistance characteristic of the FET 12 and generate a polygonal line function such that the detection output of the detection unit becomes a straight line with respect to the heating temperature. It is configured in. That is, since the change characteristic of the output with respect to the temperature of the temperature detecting means such as a thermocouple, that is, the non-linear characteristic is known, it is easy to approximate the voltage compensating for this characteristic with a broken line.

Reference numeral 13 is an amplifier which divides the output voltage of the amplifier 6 by the resistor R ₀ and the FET 12 and sends the divided voltage of the FET 12 to a data processing device (not shown).

Reference numeral 14 in the drawing is an adjustment circuit for adjusting the bias voltage input to the gate in order to correct the variation in the characteristics of the FETs connected to it.

In the apparatus thus configured, when the heating temperature of the heating furnace 1 is increased, the temperature difference voltage between the reference substance and the sample detected by the thermocouples 5 and 5'correspondingly increases the FET 12 via the amplifier 6. Is input to the source electrode of. On the other hand, the increasing sample temperature voltage detected from the thermocouple 5 is input to the linear function voltage generators 8 to 10 via the amplifier 7. As a result, as shown by the characteristic curve C in FIG. 2 (C), until the output voltage of the amplifier 7 reaches V ₁ , the resistances R _{1 to} R ₃ , R _{4 to} R ₆ , R _{7 to}
A current is shunted to the parallel circuit of R ₉ and a linear voltage is output, and while the voltage is between V ₁ and V ₂ , the diodes D and D of the operational amplifier OP ₁ are conducted to form a parallel circuit with the resistor R ₂ , As a result, the combined resistance decreases, the voltage increase rate decreases, and the voltage is output. Next, between the voltages V ₂ and V ₃ , the diodes D, D of the operational amplifier OP ₂ are turned on to form a parallel circuit with the resistor R _5, and the voltage whose rate of voltage increase is further reduced is output by further reduction of the combined resistance. , And finally the operational amplifier OP ₃ between voltage V ₃ and V ₄
The diodes D 1 and D 2 are turned on to form a parallel circuit with the ₈ resistor R, and a voltage with a reduced voltage increase rate is output. In this way, the polygonal function voltage generators 8 to 10 logarithmically compress the voltage amplitude of 0 to V ₄ and input it to the gate of the FET 12 via the amplifier 11, so that the gate input voltage of the FET T12 is shown in FIG. As shown by the characteristic curve C ′ in (B), the voltage region width is 0 to 0 as compared with the case where a linear gate voltage 0 to V _n is input.
The reduction rate of V ₄ is controlled by the logarithmically compressed voltage indicated by the characteristic curve C ′ while being reduced to V ₄ and the increase rate of the internal resistance located in the area width is symmetrical with the detection output characteristic curve a (FIG. 2). The characteristic curve b'shown in A) is corrected.

Therefore, when the peak output due to the absorption and heat generation of the sample output from the amplifier 6 is input to the FET 12, the divided voltage of the product of the peak current and the corrected internal resistance is output to the amplifier 13. Since the divided voltage increases as the heating temperature rises, the peak output that decreases as the heating temperature rises is corrected.

In the present embodiment, the case where the detection output characteristic correction device of the detection unit is applied to the differential scanning calorimeter is described, but this correction device is also applicable to the differential thermal analysis device, and the polygonal function voltage generator is also applicable. The number may be appropriately increased or decreased according to the desired degree of inclination of the broken line voltage and the degree of roughness. Further, in this embodiment, the voltage increase rate of the polygonal line function generator is logarithmically compressed so as to decrease, but it is also possible to increase the voltage increase rate by the connecting direction of the diodes.

(Effect of the Invention) As described above, according to the present invention, the differential thermal temperature voltage from the detection means whose detection output decreases as the heating temperature rises is input to the variable resistance means, and the sample temperature from the detection means is input. The voltage is input to the linear function voltage generating means, and the logarithmically compressed nonlinear voltage whose voltage increase rate decreases as the sample temperature voltage increases is input as the control voltage to the control pole of the variable resistance means. The width of the control voltage area input to the control pole of the resistance means is reduced, and the internal resistance of the variable resistance means located within this area width is formed so as to exhibit a characteristic symmetrical with the detection output characteristic of the detection means. Therefore, the peak output indicating the absorption and heat generation of the sample can be corrected without being affected by the temperature dependence of the detection means, and therefore accurate thermal analysis can be performed. It

[Brief description of drawings]

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention, and FIG. 2 (A) is a diagram showing an output characteristic curve of detection of heat absorption and generation of thermocouple and a corrected internal resistance characteristic curve of FET. 6C is an uncorrected internal resistance characteristic curve of the FET and an output voltage waveform from the linear function voltage generator, and FIG. 6C is a diagram showing an output voltage waveform of the linear function voltage generator. 1 ... Heating furnace, 5, 5 ... Thermocouple, 8, 7, 9 ... Line function voltage generator, 12 ... FET

Claims (1)

[Claims] 1. A detection means having a characteristic that the temperature difference between the reference substance and the sample and the temperature of the sample are output separately, and the detection output of the amount of heat decreases as the temperature of the heating furnace increases, A linear function voltage generating means for outputting as a control voltage a non-linear voltage that changes in response to an increase in the voltage indicating the temperature of the sample from the detecting means, and a temperature difference between the reference substance and the sample output from the detecting means. It has a function of dividing the voltage, receives the control voltage from the polygonal line function voltage generating means, and converts the internal resistance into a characteristic symmetrical with the detection output characteristic of the detecting means corresponding to the amplitude of the control voltage. And a variable resistance means.