CN1012845B - thermal analysis device - Google Patents

Abstract

A thermal analysis device having a compensation device at the output. There is a broken-line function voltage generating device that outputs a nonlinear voltage that changes with the sample temperature voltage output by the detection device. At the same time, there is no multiplication device, which multiplies the broken line function voltage with the temperature difference voltage detected by the detection device, or a voltage divider, which uses the broken line function voltage as the control voltage to generate a variable impedance device symmetrical to the sensitivity characteristics of the detection device. Divide the temperature difference voltage output by the detection device. The temperature dependence of detection sensitivity can be compensated with the present invention, enabling correct thermal analysis.

Description

The invention relates to a thermal analysis device provided at the output with compensating means for compensating the temperature dependence of the detection sensitivity of the detection means.

For example, heat flow type differential calorimeters are often used for analysis of state changes of polymer substances. In this device, the sample container inserted into the sample and the standard container inserted into the standard substance are placed on a heat transfer plate placed in a heating furnace, and heated at a certain rate of temperature rise, and the heat absorbed by the sample occurs during this process. The transmission and reception of heat energy caused by the heating phenomenon is carried out through the heat transfer plate, and at the same time, the differential heat detected by the detection device composed of two thermocouples is measured.

In this device, since the thermal conductivity of the heat transfer plate that transmits and receives heat energy changes as the temperature rises, and the heat transfer is also affected by factors such as radiation and convection corresponding to the ambient temperature, the two thermocouples constitute The detection sensitivity of the detection device to the heat absorption and heat generation of the sample shows a characteristic that decreases with the increase of the heating temperature. Therefore, the amplitude of the peak waveform representing the heat absorption and heat generation of the sample decreases as the heating temperature increases. Therefore, although the heating furnace is covered with glossy soaking bricks to prevent the detection device from being overheated, since the heating temperature of the heating furnace is raised at a certain speed while the measurement is performed, it is not Probably not related to changes in ambient temperature, so the problem of the amplitude of the output peak waveform changing with temperature still exists.

In view of the above problems, it is an object of the present invention to provide an improved thermal analysis device whose detection sensitivity is compensated at the output of the detection device so that it is not affected by the ambient temperature.

That is to say, the feature of the present invention is: be provided with detecting device and broken-line function voltage generating device, detecting device will show that the temperature difference and sample temperature of the standard substance that the heat detection sensitivity of heating furnace heating temperature rises and reduce characteristic and sample temperature respectively, The broken-line function voltage generating device outputs a nonlinear voltage that changes with the increase of the sample temperature voltage output by the above-mentioned detection device. At the same time, it also has a multiplication device or a voltage divider. The voltage is multiplied with the temperature difference voltage of the standard substance detected by the above-mentioned detection device and the sample. The voltage divider uses the voltage generated by the above-mentioned broken-line function voltage generator as the control voltage, and its internal resistance can change with the amplitude of the above-mentioned control voltage. The variable impedance device, which is symmetrical to the detection sensitivity characteristic of the detection device, divides the temperature difference voltage between the standard substance and the sample output by the detection device.

While the thermal detection sensitivity decreases with the increase of the heating temperature of the heating furnace, the temperature difference voltage between the standard substance and the sample detected by the detection device is output to the multiplication device, and the voltage increase rate is increased with the temperature and voltage of the sample detected by the detection device. The changing nonlinear voltage is the compensation voltage, which is also output to the multiplication device. By multiplying the compensation voltage with the temperature difference voltage between the standard substance and the sample, the reduction of the peak area of the temperature difference voltage between the standard substance and the sample is compensated.

In addition, the above-mentioned non-linear voltage is used as the control voltage to output to the control electrode of the variable impedance device, and through the control voltage, the internal resistance of the variable impedance device obtains a characteristic that is symmetrical to the detection sensitivity of the detection device, thereby outputting the compensated The temperature difference voltage between the standard substance and the sample affected by the thermal detection sensitivity of the detection device.

Figure 1 is a structural diagram of an embodiment of the present invention, Figure 2 (A) is a heat detection sensitivity characteristic curve of a thermocouple and peak waveforms of heat absorption and heat generation, and Figure 2 (B) is a broken line function voltage Generator output voltage waveform diagram.

Fig. 3 is a structural diagram of another embodiment device of the present invention, and Fig. 4 (A) is a thermal The heat detection sensitivity characteristic curve of the heat absorption and heat generation of the galvanic couple and the internal resistance characteristic curve after compensation by the field effect transistor. Figure 4 (B) is the internal resistance characteristic curve and the broken line function without compensation by the field effect transistor The output voltage waveform diagram of the voltage generator. In the picture:

1...Heating furnace

5, 5'... thermocouple

10, 8, 9... Broken-line function voltage generator

12...Multiplier

15...field effect transistor

Hereinafter, the present invention will be described in detail according to the embodiments shown in the drawings.

What accompanying drawing represents all is the embodiment of the present invention, and the symbol 1 among the 1st figure is a heating furnace, wherein the heat transfer plate 2 made of materials such as copper is housed, the sample container 3 that inserts sample and the standard container that inserts standard substance 4 placed on the heat transfer plate 2, meanwhile, the heat transfer plate 2 is also equipped with thermocouples 5 and 5′ for detecting the temperature of the sample and the temperature of the standard substance and outputting the temperature difference between the sample temperature and the standard substance and the sample respectively, As shown in the characteristic curve a of Fig. 2(A), the heat detection sensitivity of the thermocouples 5 and 5' decreases as the heating temperature rises. In addition, in Figure 2 (A), the peak waveform C of the temperature difference voltage between the standard substance and the sample represented by the solid line during the heat absorption and heat generation process of the sample is the compensation for the reduction of the peak area due to the influence of the heat detection sensitivity For the previous waveform, the dashed line represents the peak waveform after compensation. 6 and 7 are amplifiers, which are respectively used to amplify the temperature difference voltage between the standard substance and the sample detected by thermocouple 5 and 5′ and the temperature voltage of the sample detected by thermocouple 5′. Amplifier 6 is connected to the X terminal of multiplier 12, and amplifier 7 It is connected with the broken line function voltage generators 8-10. The structure of the broken-line function voltage generators 8-10 is: three series circuits composed of resistors R ₁ -R ₃ , R ₄ -R ₆ and R ₇ -R ₉ are connected in parallel with each other, and at the same time, the feedback loop and the output end are respectively connected with Diodes D, D. One ends of the resistors R ₂ , R ₅ and R ₈ are respectively connected to the input ends of the operational amplifiers OP ₁ , OP ₂ and OP ₃ , and their other ends are respectively connected to the output ends of the respective operational amplifiers through diodes D. Each operational amplifier adopts the inverting input mode, the positive terminal is grounded, and the bias voltages of different sizes are added to the inverting input terminals of the operational amplifiers OP ₁ ~ OP ₃ , and each bias voltage is taken from a series circuit composed of four resistors , The voltages of +15V and -15V are respectively applied to the two ends of the series circuit. As the output voltage of the amplifier 7 increases, the broken-line function voltage generators 8-10 _firstly pass through the resistance loop that connects the above-mentioned series circuits in parallel, and then sequentially make the diodes D _{, D} , _and D is turned on, output the logarithmically compressed broken line function voltage curve b shown in Figure 2 (B), and output it to the Y terminal of the multiplier 12 through the amplifier 11, and the multiplied voltage is output to the figure through the Z terminal not shown in the data processing device. In addition, these voltage generators 8-10 can output non-linear voltages with slope characteristics to compensate the heat detection sensitivity characteristics affected by the temperature difference between the standard substance and the sample.

In the device constructed in this way, if the heating temperature of the heating furnace 1 is increased, the peak areas detected by the thermocouples 5 and 5' indicated by the solid lines in Fig. 2 (A) can be correspondingly reduced by the amplifier 6. The differential thermal temperature voltage of the peak waveform C is output to the X terminal of the multiplier 12 . On the other hand, the increased sample temperature voltage detected by the thermocouple 5 is output to the broken-line function voltage generators 8-10 through the amplifier 7. Thus, before the output voltage of the amplifier 7 reaches _V1 , the current is shunted through the parallel circuit composed of resistors _R1 - _R3 , _R4 - _R6 and _R7 - _R9 , and the output voltage of Figure 2 (B) is The linear voltage shown in the characteristic curve b, during the period when the voltage changes from V ₁ to V ₂ , the diodes D and D of the operational amplifier OP ₁ are turned on to form a circuit connected in parallel with the resistor R ₂ , so that the combined resistance decreases and the output The voltage increase rate decreases; secondly, during the voltage change from _V2 to _V3 , the diodes D and D of the operational amplifier _OP2 are turned on to form a circuit connected in parallel with the resistor _R5 , and the combined resistance is further reduced, so the output voltage increases The rate is further reduced; finally, during the voltage change from _V3 to _V4 , the diodes D and D of the operational amplifier _OP3 are turned on, forming a circuit connected in parallel with the resistor _R8 , and the output voltage increase rate is further reduced. The logarithmic compressed voltage of the broken-line function voltage generators 8-10 is used as the compensation voltage, which is output to the Y terminal of the multiplier 12 through the amplifier 11 . Since the compensation voltage output by the broken-line function voltage generators 8-10 increases with the rise of the sample temperature voltage, in the multiplier 12, whenever the amplitude of the differential thermal temperature represented by the solid line is input, the peak waveform C At this time, the compensation voltage value at this time is used as a coefficient to multiply the amplitude value of the peak waveform C, thereby compensating the peak waveform C with a reduced amplitude to a waveform with an increased amplitude indicated by a dotted line, and then outputting it through the positive terminal .

Next, another embodiment of the present invention will be described.

Fig. 3 is a device of another embodiment of the present invention, and the same parts as Fig. 1 are marked with the same symbols.

In this embodiment, the amplifier 6 is connected to the source of the field effect transistor (FET) 15 through the resistor R ₀ , and the field effect transistor 15 has the internal resistance shown in the characteristic curve d of Fig. ˜Vn increases rapidly linearly, and the broken line function voltage generators 8 ˜ 10 are connected to the gate of the field effect transistor 15 through the amplifier 11 . In addition, the structure of the broken-line function voltage generators 8-9 considers the detection sensitivity characteristics of the detection components and the gate bias and internal resistance characteristics of the field effect transistor 15, so that the detection sensitivity of the detection components can be linearly related to the heating temperature. The broken line function voltage.

13 is an amplifier, which outputs the divided voltage of the field effect transistor 15 to a data processing device not shown in the figure after the output voltage of the amplifier 6 is divided by the resistor _R0 and the field effect transistor 15. In addition, the symbol 14 in the figure is an adjustment circuit added to compensate the characteristic deviation of the field effect transistor, and is used to adjust the bias voltage output to the gate.

In the device constructed in this way, if the heating temperature of the heating furnace 1 is increased, the temperature difference voltage between the standard substance and the sample detected by the thermocouples 5 and 5 ′ is output to the source of the field effect transistor 15 through the amplifier 6 accordingly. On the other hand, the increased sample temperature voltage detected by the thermocouple 5 is output to the broken-line function voltage generators 8-10 through the amplifier 7. Thus, before the output voltage of the amplifier 7 reaches _V1 , the current is shunted through the parallel circuit composed of resistors _R1 ~ _R3 , _R4 ~ _R6 and _R7 ~ _R9 , and outputs the For the linear voltage shown in the characteristic curve b, during the period when the voltage changes from V ₁ to V ₂ , the diodes D and D of the operational amplifier OP ₁ are turned on to form a loop connected in parallel with the resistor R ₂ , thereby reducing the combined resistance, so , the output voltage increase rate decreases. Thereafter, during the period when the voltage changes from _V2 to _V3 , the diodes D and D of the operational amplifier _OP2 are turned on, forming a loop connected in parallel with the resistor _R5 , and the combined resistance is further reduced, so the output voltage increase rate is further reduced, Finally, during the period when the voltage changes from _V3 to _V4 , the diodes D and D of the operational amplifier _OP3 are turned on, forming a loop connected in parallel with the resistor _R8 , and the output voltage increase rate is further reduced. In this way, since the broken-line function voltage generators 8-10 compress the voltage amplitude logarithmically into a voltage of 0- _V4 through the amplifier 11 and then add it to the gate of the field effect transistor 15, so, as shown in Figure 4 (B) As shown in the characteristic curve e of the field effect transistor, compared with the case where the input linear gate voltage is 0-Vn, the voltage range of the field effect transistor is reduced to 0-V ₄ , and at the same time, the internal resistance increase rate in this range is also affected by the above-mentioned characteristic curve The voltage control after logarithmic compression represented by e, so the detection sensitivity characteristic curve is compensated to the characteristic curve α' shown in Fig. 4 (A) which is symmetrical to a in Fig. 2 (A).

Therefore, if the peak power of the heat absorption and heat generation of the sample output with the amplifier 6 is output to the field effect transistor 15, the divided voltage after the multiplication of the peak current and the compensated internal resistance is output to the amplifier 13, because the The partial pressure increases with increasing heating temperature, so the decrease in peak power with increasing heating temperature can be compensated.

In addition, although it is described in this embodiment that the detection sensitivity compensating device of the detection part is applied to the differential scanning calorimetry device, this compensating device can also be applied to the differential thermal analysis device, and the broken line function voltage The number of generators can be appropriately increased or decreased according to the desired slope of the broken-line voltage. In addition, although in this embodiment the broken line function voltage generator is reduced logarithmically in accordance with the voltage increase rate However, by changing the connection direction of the diode, it can also be made to increase the voltage increase rate.

As mentioned above, since the present invention multiplies the temperature difference voltage between the standard substance and the sample output by the detection device with the non-linear voltage whose output voltage increase rate of the broken-line function voltage generator changes as the compensation voltage, so even if the detection device The thermal detection sensitivity decreases with the increase of the heating current, and thus the amplitude of the temperature difference voltage between the standard substance and the sample decreases, and the amplitude of the temperature difference voltage between the standard substance and the sample can also be increased by multiplying the above-mentioned compensation voltage. Therefore, it is possible to output the temperature difference voltage between the standard substance and the sample, which is not affected by the temperature dependence of the detection device, and perform accurate thermal analysis.

In addition, since the temperature and voltage of the sample detected by the detection device is input to the broken line function voltage generator, and the nonlinear voltage after logarithmic compression whose voltage increase rate decreases with the increase of the sample temperature and voltage is output as the control voltage to the variable The control pole of the impedance device, so the control voltage range applied to the control pole of the variable impedance device is narrowed, and the internal resistance of the variable impedance device within this range can be formed to be symmetrical with the detection sensitivity characteristics of the above-mentioned detection device , Therefore, the peak power indicating the heat absorption and heat generation of the sample can be compensated so as not to be affected by the temperature dependence of the detection device, thereby enabling accurate thermal analysis.

Claims (1)

1, a kind of apparatus for thermal analysis is characterized in that comprising: pick-up unit, the heat detection sensitivity is exported to a multiplying device respectively with the rise standard substance that reduces and the temperature difference and the sample temperature of sample of the heating-up temperature of heating furnace; The polygronal function device for generating voltage, the non-linear voltage that will change with the increase of the sample temperature voltage of above-mentioned detection device output is also exported to described multiplying device; Multiplying device or bleeder mechanism, described multiplying device carries out multiplying to the voltage that above-mentioned polygronal function device for generating voltage produces with the standard substance of above-mentioned detection device detection and the thermoelectric voltage of sample, the voltage that bleeder mechanism produces with above-mentioned broken line device for generating voltage is control voltage, by variable impedance apparatus the standard substance of above-mentioned detection device output and the thermoelectric voltage of sample are carried out dividing potential drop, the internal resistance of variable impedance apparatus can be transformed to the characteristic that has with the detection sensitivity characteristic symmetry of above-mentioned detection device with the amplitude of above-mentioned control voltage.

Images