High-precision temperature control system

Abstract

The invention discloses a high-precision temperature control system, which comprises a temperature control circuit, a main temperature sensor and at least one auxiliary temperature sensor, and is characterized in that the temperature control circuit is respectively connected with the main temperature sensor and each auxiliary temperature sensor; the high-precision temperature control system is used for controlling a heating sheet of the gas chamber; the main temperature sensor is arranged at a main temperature measuring point of the gas chamber, and each auxiliary temperature sensor is arranged at a corresponding auxiliary temperature measuring point of the gas chamber; the main temperature measuring point and the auxiliary temperature measuring points are uniformly distributed on the inner wall of the gas chamber; the temperature control circuit comprises a power supply circuit, a temperature detection circuit, a constant current source circuit, a heating sheet control circuit and a fan control circuit. According to the high-precision temperature control system provided by the invention, the precision and the stability of temperature detection can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature control, and relates to a temperature control system, and in particular to a high-precision temperature control system applicable to gas chamber temperature control. Background Art

[0002] The gas chamber needs to detect the temperature in real time and quickly control the temperature inside the gas chamber. Generally, the temperature control requirements for gas detection are high. Temperature changes will significantly affect the stability and accuracy of the detection equipment. In addition, some low-concentration components in the atmosphere, such as organic gases, have their optimal detection environment. Temperature changes will change the various parameters of the gas, resulting in deviations in the measurement results.

[0003] Under normal circumstances, the gas chamber temperature measurement solution mostly uses PT100 temperature measurement, which has general accuracy and the measured temperature is about ±1°C. After being processed by the front-end voltage divider op amp, the introduced coupling noise further affects the stability of the measurement; usually the volume of the gas chamber is large, and a single temperature measurement point cannot well reflect the overall temperature value inside the gas chamber at the current time, which will affect the measurement results in a temperature-sensitive environment.

[0004] In view of this, there is an urgent need to design a new temperature control system to overcome at least some of the above-mentioned defects of the existing temperature control systems. Summary of the invention

[0005] The present invention provides a high-precision temperature control system, which can improve the accuracy and stability of temperature detection.

[0006] To solve the above technical problem, according to one aspect of the present invention, the following technical solution is adopted:

[0007] A high-precision temperature control system, the high-precision temperature control system comprising: a temperature control circuit, a main temperature sensor and at least one auxiliary temperature sensor, the temperature control circuit being connected to the main temperature sensor and each auxiliary temperature sensor respectively;

[0008] The high-precision temperature control system is used to control the heating plate of the gas chamber; the main temperature sensor is arranged at the main temperature measuring point of the gas chamber, and each auxiliary temperature sensor is arranged at the corresponding auxiliary temperature measuring point of the gas chamber; the main temperature measuring point and each auxiliary temperature measuring point are evenly distributed on the inner wall of the gas chamber;

[0009] The main temperature sensor is used to control the power of the heating plate, and each auxiliary temperature sensor is used to measure the real-time temperature inside the gas chamber and output data through a weighted average algorithm; if the value detected by the main temperature sensor reaches outside the temperature control range, the temperature inside the gas chamber is changed by increasing or decreasing the power of the heating plate until the output data of all temperature measurement points meet the set value;

[0010] Multi-point temperature measurement can accurately control the temperature, and the gas chamber can have a relatively stable temperature environment. Moreover, after the sensor at a certain temperature measurement point fails, it can maintain its original function to prevent the heater from working abnormally.

[0011] The temperature control circuit includes a power supply circuit, a microprocessor, a temperature detection circuit, a constant current source circuit, a heating plate control circuit and a fan control circuit;

[0012] The microprocessor is respectively connected to the temperature detection circuit, the heating plate control circuit and the fan control circuit, and the constant current source circuit is connected to the temperature detection circuit; the power supply circuit provides the microprocessor, the temperature detection circuit, the constant current source circuit, the heating plate control circuit and the fan control circuit with the electric energy required for operation.

[0013] As an embodiment of the present invention, the power supply circuit includes a DC-DC power supply module U1, a first linear voltage regulator chip U2, a second linear voltage regulator chip U3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a first zero capacitor C10, a first first capacitor C11, a first second capacitor C12, a first resistor R1, a second resistor R2, a third resistor R3 and a first interface circuit P1;

[0014] The first power supply voltage is respectively connected to the first pin of the first interface circuit P1, the first end of the sixth capacitor C6, the first end of the seventh capacitor C7, and the eighth pin of the DC-DC power supply module U1;

[0015] The second pin of the first interface circuit P1, the second end of the sixth capacitor C6, the second end of the seventh capacitor C7, and the seventh pin of the DC-DC power supply module U1 are grounded respectively;

[0016] The second power supply voltage is respectively connected to the third pin of the DC-DC power module U1, the fourth pin of the DC-DC power module U1, the first end of the first capacitor C1, the first end of the second capacitor C2, the first end of the third capacitor C3, the first end of the first resistor R1, and the third pin of the first linear voltage regulator chip U2;

[0017] The second end of the first capacitor C1, the second end of the second capacitor C2, and the second end of the third capacitor C3 are grounded respectively; the second pin of the first linear voltage regulator chip U2 is connected to the first end of the fourth capacitor C4 and the first end of the fifth capacitor C5 respectively, and the first pin of the first linear voltage regulator chip U2, the second end of the fourth capacitor C4, and the second end of the fifth capacitor C5 are grounded respectively;

[0018] The third power supply voltage is respectively connected to the second end of the first resistor R1, the first end of the eighth capacitor C8, the first end of the ninth capacitor C9, the first pin of the second linear voltage regulator chip U3, the second pin of the second linear voltage regulator chip U3, and the third pin of the second linear voltage regulator chip U3; the second end of the eighth capacitor C8 and the second end of the ninth capacitor C9 are grounded respectively;

[0019] A first end of the third resistor R3 is grounded, and a second end of the third resistor R3 is grounded;

[0020] The fourth power supply voltage is respectively connected to the ninth pin of the second linear voltage regulator chip U3, the first zero pin of the second linear voltage regulator chip U3, the first end of the first zero capacitor C10, and the first end of the first first capacitor C11; the seventh pin of the second linear voltage regulator chip U3 is respectively connected to the first end of the second resistor R2 and the first end of the first second capacitor C12; the fifth pin of the second linear voltage regulator chip U3, the eighth pin of the second linear voltage regulator chip U3, the first first pin of the second linear voltage regulator chip U3, the second end of the second resistor R2, the second end of the first second capacitor C12, the second end of the first zero capacitor C10, and the second end of the first first capacitor C11 are respectively grounded.

[0021] As an embodiment of the present invention, the DC-DC power supply module U1 supports a wide power input of 10-48V, a maximum output current of 0.7A, and has a small size, high output efficiency, and small ripple; capacitors C6, C7, C1, and C2 play a filtering role;

[0022] The second linear voltage regulator chip U3 uses a low-noise, ultra-high PSRR linear voltage regulator chip, which can provide a clean power supply to the analog-to-digital conversion chip alone; the second resistor R2 sets the output voltage of the second linear voltage regulator chip U3, and the SET end of the second linear voltage regulator chip U3 provides a precision current of 100uA. out =R2*I SET .

[0023] As an embodiment of the present invention, the high-precision temperature control system includes a four-wire external platinum thermal resistor RTD, the platinum thermal resistor RTD as a main temperature sensor and at least one auxiliary temperature sensor;

[0024] A main temperature measuring point and three auxiliary temperature measuring points are provided in the gas chamber, and platinum thermal resistors RTD are respectively connected to the main temperature measuring point and the auxiliary temperature measuring points; the platinum thermal resistor RTD is connected to the temperature measuring points through four cables, and the four cables form four line resistances, which are respectively recorded as the first line resistance RL1, the second line resistance RL2, the third line resistance RL3, and the fourth line resistance RL4; the platinum thermal resistors RTD are respectively connected to the first end of the first line resistance RL1, the first end of the second line resistance RL2, the first end of the third line resistance RL3, and the first end of the fourth line resistance RL4; the second end of the first line resistance RL1 is connected to the current source;

[0025] The temperature detection circuit includes an analog-to-digital conversion chip U4, a first third capacitor C13, a first fourth capacitor C14, a first fifth capacitor C15, a first sixth capacitor C16, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7;

[0026] The fifth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fourth resistor R4, the first end of the first third capacitor C13, and the first end of the first fourth capacitor R14, the first end of the fourth resistor R4 is connected to the second end of the second line resistor RL2, and the second end of the first third capacitor C13 is grounded;

[0027] The eighth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fifth resistor R5, the second end of the first fifth capacitor C15, and the second end of the first fourth capacitor C14, the first end of the fifth resistor R5 is connected to the second end of the third line resistor RL3, and the first end of the first fifth capacitor C15 is grounded;

[0028] The first and second pins of the analog-to-digital conversion chip U4 are respectively connected to the first end of the sixth resistor R6, the first end of the first capacitor C16, and the second end of the fourth line resistor RL4;

[0029] The first three pins of the analog-to-digital conversion chip U4 are respectively connected to the second end of the sixth resistor R6, the second end of the first capacitor C16, and the first end of the seventh resistor R7, and the second end of the seventh resistor R7 is grounded.

[0030] As an embodiment of the present invention, the temperature detection circuit is connected to a four-wire external RTD; the core of the detection is to use a 24-bit integrated analog-to-digital converter to provide high-precision integrated four-wire PT1000 platinum thermal RTD measurement. The analog-to-digital conversion chip U4 integrates PGA and reference voltage source internally, supports differential and pseudo-differential inputs, and the power supply AVDD and IOVDD take 3.3V from the analog power supply U3 and the digital power supply U2 respectively. The sampling results are connected to the single-chip microcomputer through SPI communication. The four-wire RTD only needs one precision current source. The current flows through the four lines L1 and L4, and a voltage is generated at both ends of the RTD. It is connected to the differential input of the analog-to-digital converter through L2 and L3, which can completely eliminate the influence of line resistances RL1, RL2, RL3, and RL4. At the same time, PT1000 can improve the voltage accuracy by 10 times compared with PT100, and the temperature measurement accuracy reaches 0.05℃. In Figure c-1, L1 and L2 of the RTD are connected to one end, and L3 and L4 are connected to the other end. The current IOUT flows through RL1, RTD, RL4, R6, and R7. At this time, the voltage V RTD =I OUT*RTD; AIN1 and AIN2 are configured as differential input terminals, L2 is connected to AIN1 through RC filtering of R4 and C13, and C14 is used as common mode filtering. L32 is connected to AIN2 through RC filtering of R5 and C15, and C14 is used as common mode filtering. The voltage between AIN1 and AIN2 is input. The current IOUT flows through the precision reference resistor R6 at the same time. At this time, V R6 =I OUT *R6, R6 is connected to REFIN1+ and REFIN1- as the reference voltage input.

[0031] Comparing the differential voltage with the reference voltage gives: V RTD / V R6 =(I OUT *RTD) / (I OUT *R6)=RTD / R6, the measurement result is related to the accuracy of R6, and the influence of line resistance is completely eliminated. The analog-to-digital converter U4 supports four-way differential input, and can support the series measurement of four four-wire PT1000s with a single constant current source without affecting the accuracy and stability; as shown in Figure c-2, the more measurement points, the more accurate the temperature control, and the analog-to-digital conversion chip used can provide 8-way differential input signals, which can measure the temperature of 8 temperature measurement points at the same time.

[0032] As an implementation mode of the present invention, the constant current source circuit includes a first operational amplifier U5, a second operational amplifier U6, a digital-to-analog converter U7, an eighth resistor R8, a ninth resistor R9, a first zero resistor R10, a first first resistor R11, and a first second resistor R12;

[0033] The sixth pin of the digital-to-analog converter U7 is connected to the first end of the first zero resistor R10, the second end of the first zero resistor R10 is respectively connected to the non-inverting input end of the first operational amplifier U5 and the first end of the first resistor R11; the second end of the first resistor R11 is respectively connected to the inverting input end of the second operational amplifier U6 and the output end of the second operational amplifier U6;

[0034] The inverting input terminal of the first operational amplifier U5 is respectively connected to the second end of the eighth resistor R8 and the first end of the ninth resistor R9, and the first end of the eighth resistor R8 is grounded;

[0035] The output end of the first operational amplifier U5 is connected to the second end of the ninth resistor R9 and the first end of the second resistor R12 respectively, and the second ends of the first and second resistors R12 are connected to the non-inverting input end of the second operational amplifier U6.

[0036] As an implementation mode of the present invention, the digital-to-analog converter U7 outputs a programmable voltage value VOUT, which is input to the non-inverting input terminal of the differential operational amplifier U5. The output terminal of the operational amplifier U5 is connected to the precision resistor R12, and the precision resistor R12 is connected to the non-inverting input terminal of the operational amplifier U6. The operational amplifier U6 builds a voltage follower, and the output terminal is connected to the REF terminal of the differential operational amplifier U6. At this time:

[0037]

[0038] And R8=R9=R10=R11, then

[0039] Among them, VOUT is the output terminal of the differential operational amplifier. Due to the low offset voltage, low gain error and integrated resistance of the differential operational amplifier U5, as well as the extremely high common-mode rejection ratio, it can output a high-precision voltage value; the operational amplifier U6 feeds back the voltage generated by IOUT flowing through the load to the REF terminal of the differential operational amplifier U5, so that the circuit can quickly establish and output a stable current source; the digital-to-analog converter U7 adopts a 20-bit model, and the size of the current source can be changed by changing the output accurate voltage of the digital-to-analog converter.

[0040] As an implementation mode of the present invention, in order to make the platinum thermal resistor RTD and temperature have an approximately linear conversion relationship, the temperature range is divided into multiple intervals, and the corresponding relationship between the resistance and temperature in each interval is linear. The more intervals there are, the higher the accuracy. The resistance of the RTD is found out by an algorithm to find the corresponding interval, and then the temperature is calculated by segmented interpolation.

[0041] The temperature range is divided into multiple intervals, and the binary search method is used to find the temperature interval in which the measured resistance value is located. The principle is to divide all temperature values ​​into half and take the middle value, compare the measured resistance value and the middle value, and then put it into the other half, and repeat the middle value for comparison until the corresponding temperature interval is found; the recursive algorithm can be used in the program. The temperature interval is selected as 1°C, that is, a calibration point is taken every 1°C, and the linear equation fitted by the two calibration points, the measured resistance value is in a certain interval, and the current temperature value can be calculated. Using this algorithm requires the establishment of a resistance-temperature graduation table.

[0042] The beneficial effect of the present invention is that the high-precision temperature control system proposed by the present invention can improve the accuracy and stability of temperature detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of a usage scenario of a high-precision temperature control system in one embodiment of the present invention.

[0044] Figure 2 Schematic diagram of the composition of a temperature control circuit in one embodiment of the present invention.

[0045] Figure 3 FIG. 4 is a circuit diagram of a power supply circuit in an embodiment of the present invention.

[0046] Figure 4 FIG. 4 is a circuit diagram of a temperature detection circuit in an embodiment of the present invention.

[0047] Figure 5Schematic diagram of multi-channel temperature measurement in a gas chamber in one embodiment of the present invention.

[0048] Figure 6 FIG. 4 is a circuit diagram of a constant current source circuit in one embodiment of the present invention.

[0049] Figure 7 It is a schematic diagram of interpolation calculation of temperature in one embodiment of the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0051] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0052] The description in this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The same or similar prior art means and some technical features in the embodiments are mutually replaced within the scope of the present invention.

[0053] The description of the steps in each embodiment in the specification is only for the convenience of explanation, and the implementation method of the present application is not limited by the order of implementation of the steps.

[0054] The term "connection" as used in the specification includes both direct connection and indirect connection, such as connection through some active devices, passive devices or electrically conductive media; it may also include connection through other active devices or passive devices known to those skilled in the art on the basis of achieving the same or similar functional purposes, such as connection through circuits or components such as switches and follower circuits.

[0055] The present invention discloses a high-precision temperature control system. Figure 1 This is a schematic diagram of a use scenario of a high-precision temperature control system in one embodiment of the present invention; please refer to Figure 1 The high-precision temperature control system includes: a temperature control circuit, a main temperature sensor 1 and at least one auxiliary temperature sensor 2, the temperature control circuit is respectively connected to the main temperature sensor 1 and each auxiliary temperature sensor 2; the high-precision temperature control system is used to control the heating plate 3 of the gas chamber 4; the main temperature sensor 1 is arranged at the main temperature measuring point of the gas chamber 4, and each auxiliary temperature sensor 2 is arranged at the corresponding auxiliary temperature measuring point of the gas chamber 4; the main temperature measuring point 1 and each auxiliary temperature measuring point 2 are evenly distributed on the inner wall of the gas chamber 4.

[0056] The main temperature sensor 1 is used to control the power of the heating plate 3, and each auxiliary temperature sensor 2 is used to measure the real-time temperature inside the gas chamber 4 and output data through a weighted average algorithm; if the value detected by the main temperature sensor 1 is outside the temperature control range, the internal temperature of the gas chamber 4 is changed by increasing or decreasing the power of the heating plate until the output data of all temperature measurement points meet the set value. Multi-point temperature measurement can accurately control the temperature, and the gas chamber can have a relatively stable temperature environment. Moreover, after the sensor at a certain temperature measurement point fails, it can maintain its original function to prevent the heating plate from working abnormally;

[0057] Figure 2 FIG. 1 is a schematic diagram of the composition of a temperature control circuit in an embodiment of the present invention; please refer to FIG. Figure 2 The temperature control circuit includes a power supply circuit 5, a microprocessor 6, a temperature detection circuit 7, a constant current source circuit 8, a heating plate control circuit 9 and a fan control circuit 10. The microprocessor 6 is connected to the temperature detection circuit 7, the heating plate control circuit 9 and the fan control circuit 10 respectively, and the constant current source circuit 8 is connected to the temperature detection circuit 7; the power supply circuit 5 provides the microprocessor 6, the temperature detection circuit 7, the constant current source circuit 8, the heating plate control circuit 9 and the fan control circuit 10 with the electric energy required for their operation.

[0058] Figure 3 is a circuit diagram of a power supply circuit in one embodiment of the present invention; please refer to Figure 3 In one embodiment of the present invention, the power supply circuit includes a DC-DC power supply module U1, a first linear voltage regulator chip U2, a second linear voltage regulator chip U3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a first zero capacitor C10, a first first capacitor C11, a first second capacitor C12, a first resistor R1, a second resistor R2, a third resistor R3 and a first interface circuit P1;

[0059] The first power supply voltage is respectively connected to the first pin of the first interface circuit P1, the first end of the sixth capacitor C6, the first end of the seventh capacitor C7, and the eighth pin of the DC-DC power supply module U1;

[0060] The second pin of the first interface circuit P1, the second end of the sixth capacitor C6, the second end of the seventh capacitor C7, and the seventh pin of the DC-DC power supply module U1 are grounded respectively;

[0061] The second power supply voltage is respectively connected to the third pin of the DC-DC power module U1, the fourth pin of the DC-DC power module U1, the first end of the first capacitor C1, the first end of the second capacitor C2, the first end of the third capacitor C3, the first end of the first resistor R1, and the third pin of the first linear voltage regulator chip U2;

[0062] The second end of the first capacitor C1, the second end of the second capacitor C2, and the second end of the third capacitor C3 are grounded respectively; the second pin of the first linear voltage regulator chip U2 is connected to the first end of the fourth capacitor C4 and the first end of the fifth capacitor C5 respectively, and the first pin of the first linear voltage regulator chip U2, the second end of the fourth capacitor C4, and the second end of the fifth capacitor C5 are grounded respectively;

[0063] The third power supply voltage is respectively connected to the second end of the first resistor R1, the first end of the eighth capacitor C8, the first end of the ninth capacitor C9, the first pin of the second linear voltage regulator chip U3, the second pin of the second linear voltage regulator chip U3, and the third pin of the second linear voltage regulator chip U3; the second end of the eighth capacitor C8 and the second end of the ninth capacitor C9 are grounded respectively; the first end of the third resistor R3 is grounded, and the second end of the third resistor R3 is grounded;

[0064] The fourth power supply voltage is respectively connected to the ninth pin of the second linear voltage regulator chip U3, the first zero pin of the second linear voltage regulator chip U3, the first end of the first zero capacitor C10, and the first end of the first first capacitor C11; the seventh pin of the second linear voltage regulator chip U3 is respectively connected to the first end of the second resistor R2 and the first end of the first second capacitor C12; the fifth pin of the second linear voltage regulator chip U3, the eighth pin of the second linear voltage regulator chip U3, the first first pin of the second linear voltage regulator chip U3, the second end of the second resistor R2, the second end of the first second capacitor C12, the second end of the first zero capacitor C10, and the second end of the first first capacitor C11 are respectively grounded.

[0065] In one embodiment of the present invention, the DC-DC power supply module U1 supports a wide power input of 10-48V, a maximum output current of 0.7A, and has a small size, high output efficiency, and small ripple; capacitors C6, C7, C1, and C2 play a filtering role;

[0066] The second linear voltage regulator chip U3 uses a low-noise, ultra-high PSRR linear voltage regulator chip, which can provide a clean power supply to the analog-to-digital conversion chip alone; the second resistor R2 sets the output voltage of the second linear voltage regulator chip U3, and the SET end of the second linear voltage regulator chip U3 provides a precision current of 100uA. out =R2*I SET .

[0067] As an embodiment of the present invention, the high-precision temperature control system includes a four-wire external platinum thermal resistor RTD, the platinum thermal resistor RTD as a main temperature sensor and at least one auxiliary temperature sensor;

[0068] A main temperature measuring point and three auxiliary temperature measuring points are provided in the gas chamber, and platinum thermal resistors RTD are respectively connected to the main temperature measuring point and the auxiliary temperature measuring points; the platinum thermal resistor RTD is connected to the temperature measuring points through four cables, and the four cables form four line resistances, which are respectively recorded as the first line resistance RL1, the second line resistance RL2, the third line resistance RL3, and the fourth line resistance RL4; the platinum thermal resistors RTD are respectively connected to the first end of the first line resistance RL1, the first end of the second line resistance RL2, the first end of the third line resistance RL3, and the first end of the fourth line resistance RL4; the second end of the first line resistance RL1 is connected to the current source;

[0069] The temperature detection circuit includes an analog-to-digital conversion chip U4, a first third capacitor C13, a first fourth capacitor C14, a first fifth capacitor C15, a first sixth capacitor C16, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7;

[0070] The fifth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fourth resistor R4, the first end of the first third capacitor C13, and the first end of the first fourth capacitor R14, the first end of the fourth resistor R4 is connected to the second end of the second line resistor RL2, and the second end of the first third capacitor C13 is grounded;

[0071] The eighth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fifth resistor R5, the second end of the first fifth capacitor C15, and the second end of the first fourth capacitor C14, the first end of the fifth resistor R5 is connected to the second end of the third line resistor RL3, and the first end of the first fifth capacitor C15 is grounded;

[0072] The first and second pins of the analog-to-digital conversion chip U4 are respectively connected to the first end of the sixth resistor R6, the first end of the first capacitor C16, and the second end of the fourth line resistor RL4;

[0073] The first three pins of the analog-to-digital conversion chip U4 are respectively connected to the second end of the sixth resistor R6, the second end of the first capacitor C16, and the first end of the seventh resistor R7, and the second end of the seventh resistor R7 is grounded.

[0074] Figure 4 FIG. 1 is a circuit diagram of a temperature detection circuit in an embodiment of the present invention. Figure 5 This is a schematic diagram of multi-channel temperature measurement of a gas chamber in one embodiment of the present invention; please refer to Figure 4 , Figure 5In one embodiment of the present invention, the temperature detection circuit is connected to a four-wire external RTD; the core of the detection is to use a 24-bit integrated analog-to-digital converter to provide high-precision integrated four-wire PT1000 platinum thermal RTD measurement. The analog-to-digital conversion chip U4 integrates PGA and reference voltage source internally, supports differential and pseudo-differential inputs, and the power supply AVDD and IOVDD are respectively taken from the analog power supply U3 and the digital power supply U2. 3.3V, and the sampling results are connected to the microcontroller through SPI communication. The four-wire RTD only needs one precision current source. The current flows through the four lines L1 and L4, and a voltage is generated at both ends of the RTD. It is connected to the differential input of the analog-to-digital converter through L2 and L3, which can completely eliminate the influence of line resistances RL1, RL2, RL3, and RL4. At the same time, PT1000 can improve the voltage accuracy by 10 times compared with PT100, and the temperature measurement accuracy reaches 0.05℃. In Figure c-1, L1 and L2 of the RTD are connected to one end, and L3 and L4 are connected to the other end. The current IOUT flows through RL1, RTD, RL4, R6, and R7. At this time, the voltage V RTD =I OUT *RTD; AIN1 and AIN2 are configured as differential input terminals, L2 is connected to AIN1 through RC filtering of R4 and C13, and C14 is used as common mode filtering. L32 is connected to AIN2 through RC filtering of R5 and C15, and C14 is used as common mode filtering. The voltage between AIN1 and AIN2 is input. The current IOUT flows through the precision reference resistor R6 at the same time. At this time, V R6 =I OUT *R6, R6 is connected to REFIN1+ and REFIN1- as the reference voltage input.

[0075] Comparing the differential voltage with the reference voltage gives: V RTD / V R6 =(I OUT *RTD) / (I OUT *R6)=RTD / R6, the measurement result is related to the accuracy of R6, and the influence of line resistance is completely eliminated. The analog-to-digital converter U4 supports four-way differential input, and can support the series measurement of four four-wire PT1000s with a single constant current source without affecting the accuracy and stability; as shown in Figure c-2, the more measurement points, the more accurate the temperature control, and the analog-to-digital conversion chip used can provide 8-way differential input signals, which can measure the temperature of 8 temperature measurement points at the same time.

[0076] Figure 6 is a circuit diagram of a constant current source circuit in one embodiment of the present invention; please refer to Figure 6 In one embodiment of the present invention, the constant current source circuit includes a first operational amplifier U5, a second operational amplifier U6, a digital-to-analog converter U7, an eighth resistor R8, a ninth resistor R9, a first zero resistor R10, a first first resistor R11, and a first second resistor R12;

[0077] The sixth pin of the digital-to-analog converter U7 is connected to the first end of the first zero resistor R10, the second end of the first zero resistor R10 is respectively connected to the non-inverting input end of the first operational amplifier U5 and the first end of the first resistor R11; the second end of the first resistor R11 is respectively connected to the inverting input end of the second operational amplifier U6 and the output end of the second operational amplifier U6;

[0078] The inverting input terminal of the first operational amplifier U5 is respectively connected to the second end of the eighth resistor R8 and the first end of the ninth resistor R9, and the first end of the eighth resistor R8 is grounded;

[0079] The output end of the first operational amplifier U5 is connected to the second end of the ninth resistor R9 and the first end of the second resistor R12 respectively, and the second ends of the first and second resistors R12 are connected to the non-inverting input end of the second operational amplifier U6.

[0080] As an implementation mode of the present invention, the digital-to-analog converter U7 outputs a programmable voltage value VOUT, which is input to the non-inverting input terminal of the differential operational amplifier U5. The output terminal of the operational amplifier U5 is connected to the precision resistor R12, and the precision resistor R12 is connected to the non-inverting input terminal of the operational amplifier U6. The operational amplifier U6 builds a voltage follower, and the output terminal is connected to the REF terminal of the differential operational amplifier U6. At this time:

[0081]

[0082] And R8=R9=R10=R11, then

[0083] Among them, VOUT is the output terminal of the differential operational amplifier. Due to the low offset voltage, low gain error and integrated resistance of the differential operational amplifier U5, as well as the extremely high common-mode rejection ratio, it can output a high-precision voltage value; the operational amplifier U6 feeds back the voltage generated by IOUT flowing through the load to the REF terminal of the differential operational amplifier U5, so that the circuit can quickly establish and output a stable current source; the digital-to-analog converter U7 adopts a 20-bit model, and the size of the current source can be changed by changing the output accurate voltage of the digital-to-analog converter.

[0084] In one embodiment of the present invention, if the platinum thermal resistor RTD and temperature are to have an approximately linear conversion relationship, the temperature range needs to be divided into multiple intervals, and the corresponding relationship between the resistance and temperature in each interval is linear. The more intervals there are, the higher the accuracy. The resistance of the RTD is found out by an algorithm to find the corresponding interval, and then the temperature is calculated by segmented interpolation.

[0085] The temperature range is divided into multiple intervals, and the binary search method is used to find the temperature interval in which the measured resistance value is located. The principle is to divide all temperature values ​​into half and take the middle value, compare the measured resistance value and the middle value, and then put them into the other half, and repeat the middle value comparison until the corresponding temperature interval is found; the recursive algorithm can be used in the program. The temperature interval is selected as 1℃, that is, a calibration point is taken every 1℃, and the linear equation fitted by the two calibration points. The measured resistance value is located in a certain interval, and the current temperature value can be calculated (such as Figure 7 Using this algorithm requires the establishment of a resistance-temperature graduation table.

[0086] In summary, the high-precision temperature control system proposed in the present invention can improve the accuracy and stability of temperature detection.

[0087] It should be noted that the present application can be implemented in software and / or a combination of software and hardware; for example, it can be implemented using an application-specific integrated circuit (ASIC), a general-purpose computer, or any other similar hardware device. In some embodiments, the software program of the present application can be executed by a processor to implement the above steps or functions. Similarly, the software program of the present application (including related data structures) can be stored in a computer-readable recording medium; for example, a RAM memory, a magnetic or optical drive or a floppy disk and the like. In addition, some steps or functions of the present application can be implemented in hardware; for example, as a circuit that cooperates with a processor to perform various steps or functions.

[0088] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above-mentioned embodiments. The effects or advantages involved in the embodiments may not be embodied in the embodiments due to interference from various factors, and the description of the effects or advantages is not used to limit the embodiments. The deformation and change of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent parts are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.

Claims

1. A high-precision temperature control system, characterized in that: The high-precision temperature control system comprises: a temperature control circuit, a main temperature sensor and at least one auxiliary temperature sensor, wherein the temperature control circuit is connected to the main temperature sensor and each auxiliary temperature sensor respectively; The high-precision temperature control system is used to control the heating plate of the gas chamber; the main temperature sensor is arranged at the main temperature measuring point of the gas chamber, and each auxiliary temperature sensor is arranged at the corresponding auxiliary temperature measuring point of the gas chamber; the main temperature measuring point and each auxiliary temperature measuring point are evenly distributed on the inner wall of the gas chamber; The main temperature sensor is used to control the power of the heating plate, and each auxiliary temperature sensor is used to measure the real-time temperature inside the gas chamber and output data through a weighted average algorithm; if the value detected by the main temperature sensor reaches outside the temperature control range, the temperature inside the gas chamber is changed by increasing or decreasing the power of the heating plate until the output data of all temperature measurement points meet the set value; Multi-point temperature measurement can accurately control the temperature, and the gas chamber can have a relatively stable temperature environment. Moreover, after the sensor at a certain temperature measurement point fails, it can maintain its original function to prevent the heater from working abnormally. The temperature control circuit includes a power supply circuit, a microprocessor, a temperature detection circuit, a constant current source circuit, a heating plate control circuit and a fan control circuit; The microprocessor is respectively connected to the temperature detection circuit, the heating plate control circuit and the fan control circuit, and the constant current source circuit is connected to the temperature detection circuit; the power supply circuit provides the microprocessor, the temperature detection circuit, the constant current source circuit, the heating plate control circuit and the fan control circuit with the electric energy required for operation.

2. The high-precision temperature control circuit according to claim 1, characterized in that: The power supply circuit includes a DC-DC power supply module U1, a first linear voltage regulator chip U2, a second linear voltage regulator chip U3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a first zero capacitor C10, a first first capacitor C11, a first second capacitor C12, a first resistor R1, a second resistor R2, a third resistor R3 and a first interface circuit P1; The first power supply voltage is respectively connected to the first pin of the first interface circuit P1, the first end of the sixth capacitor C6, the first end of the seventh capacitor C7, and the eighth pin of the DC-DC power supply module U1; The second pin of the first interface circuit P1, the second end of the sixth capacitor C6, the second end of the seventh capacitor C7, and the seventh pin of the DC-DC power supply module U1 are grounded respectively; The second power supply voltage is respectively connected to the third pin of the DC-DC power module U1, the fourth pin of the DC-DC power module U1, the first end of the first capacitor C1, the first end of the second capacitor C2, the first end of the third capacitor C3, the first end of the first resistor R1, and the third pin of the first linear voltage regulator chip U2; The second end of the first capacitor C1, the second end of the second capacitor C2, and the second end of the third capacitor C3 are grounded respectively; the second pin of the first linear voltage regulator chip U2 is connected to the first end of the fourth capacitor C4 and the first end of the fifth capacitor C5 respectively, and the first pin of the first linear voltage regulator chip U2, the second end of the fourth capacitor C4, and the second end of the fifth capacitor C5 are grounded respectively; The third power supply voltage is respectively connected to the second end of the first resistor R1, the first end of the eighth capacitor C8, the first end of the ninth capacitor C9, the first pin of the second linear voltage regulator chip U3, the second pin of the second linear voltage regulator chip U3, and the third pin of the second linear voltage regulator chip U3; the second end of the eighth capacitor C8 and the second end of the ninth capacitor C9 are grounded respectively; A first end of the third resistor R3 is grounded, and a second end of the third resistor R3 is grounded; The fourth power supply voltage is respectively connected to the ninth pin of the second linear voltage regulator chip U3, the first zero pin of the second linear voltage regulator chip U3, the first end of the first zero capacitor C10, and the first end of the first first capacitor C11; the seventh pin of the second linear voltage regulator chip U3 is respectively connected to the first end of the second resistor R2 and the first end of the first second capacitor C12; the fifth pin of the second linear voltage regulator chip U3, the eighth pin of the second linear voltage regulator chip U3, the first first pin of the second linear voltage regulator chip U3, the second end of the second resistor R2, the second end of the first second capacitor C12, the second end of the first zero capacitor C10, and the second end of the first first capacitor C11 are respectively grounded.

3. The high-precision temperature control circuit according to claim 2, characterized in that: The DC-DC power module U1 supports a wide power input of 10-48V, a maximum output current of 0.7A, and has a small size, high output efficiency, and small ripple; capacitors C6, C7, C1, and C2 act as filters; The second linear voltage regulator chip U3 uses a low-noise, ultra-high PSRR linear voltage regulator chip, which can provide a clean power supply to the analog-to-digital conversion chip alone; the second resistor R2 sets the output voltage of the second linear voltage regulator chip U3, and the SET end of the second linear voltage regulator chip U3 provides a precision current of 100uA. out =R2*I SET .

4. The high-precision temperature control circuit according to claim 1, characterized in that: The high-precision temperature control system includes a four-wire external platinum thermal resistor RTD, the platinum thermal resistor RTD as a main temperature sensor and at least one auxiliary temperature sensor; A main temperature measuring point and three auxiliary temperature measuring points are provided in the gas chamber, and platinum thermal resistors RTD are respectively connected to the main temperature measuring point and the auxiliary temperature measuring points; the platinum thermal resistor RTD is connected to the temperature measuring points through four cables, and the four cables form four line resistances, which are respectively recorded as the first line resistance RL1, the second line resistance RL2, the third line resistance RL3, and the fourth line resistance RL4; the platinum thermal resistors RTD are respectively connected to the first end of the first line resistance RL1, the first end of the second line resistance RL2, the first end of the third line resistance RL3, and the first end of the fourth line resistance RL4; the second end of the first line resistance RL1 is connected to the current source; The temperature detection circuit includes an analog-to-digital conversion chip U4, a first third capacitor C13, a first fourth capacitor C14, a first fifth capacitor C15, a first sixth capacitor C16, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7; The fifth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fourth resistor R4, the first end of the first third capacitor C13, and the first end of the first fourth capacitor R14, the first end of the fourth resistor R4 is connected to the second end of the second line resistor RL2, and the second end of the first third capacitor C13 is grounded; The eighth pin of the analog-to-digital conversion chip U4 is respectively connected to the second end of the fifth resistor R5, the second end of the first fifth capacitor C15, and the second end of the first fourth capacitor C14, the first end of the fifth resistor R5 is connected to the second end of the third line resistor RL3, and the first end of the first fifth capacitor C15 is grounded; The first and second pins of the analog-to-digital conversion chip U4 are respectively connected to the first end of the sixth resistor R6, the first end of the first capacitor C16, and the second end of the fourth line resistor RL4; The first three pins of the analog-to-digital conversion chip U4 are respectively connected to the second end of the sixth resistor R6, the second end of the first capacitor C16, and the first end of the seventh resistor R7, and the second end of the seventh resistor R7 is grounded.

5. The high-precision temperature control circuit according to claim 4, characterized in that: The temperature detection circuit is connected to a four-wire external RTD; the core of the detection is to use a 24-bit integrated analog-to-digital converter to provide high-precision integrated four-wire PT1000 platinum thermal RTD measurement. The analog-to-digital conversion chip U4 integrates PGA and reference voltage source, supports differential and pseudo-differential inputs, and the power supply AVDD and IOVDD are respectively taken from the analog power supply U3 and the digital power supply U2. 3.3V, and the sampling results are connected to the microcontroller through SPI communication. The four-wire RTD only needs a precision current source. The current flows through the four lines L1 and L4, and a voltage is generated at both ends of the RTD. It is connected to the differential input of the analog-to-digital converter through L2 and L3, which can completely eliminate the influence of line resistance RL1, RL2, RL3, and RL4. At the same time, PT1000 can improve the voltage accuracy by 10 times compared with PT100, and the temperature measurement accuracy reaches 0.05℃. In Figure c-1, L1 and L2 of the RTD are connected to one end, and L3 and L4 are connected to the other end. The current IOUT flows through RL1, RTD, RL4, R6, and R7. At this time, the voltage V RTD =I OUT *RTD; AIN1 and AIN2 are configured as differential input terminals, L2 is connected to AIN1 through RC filtering of R4 and C13, and C14 is used as common mode filtering. L32 is connected to AIN2 through RC filtering of R5 and C15, and C14 is used as common mode filtering. The voltage between AIN1 and AIN2 is input. The current IOUT flows through the precision reference resistor R6 at the same time. At this time, V R6 =I OUT *R6, R6 is connected to REFIN1+ and REFIN1- as the reference voltage input. Comparing the differential voltage with the reference voltage gives: V RTD / V R6 =(I OUT *RTD) / (I OUT *R6)=RTD / R6, the measurement result is related to the accuracy of R6, and the influence of line resistance is completely eliminated. The analog-to-digital converter U4 supports four-way differential input, and can support the series measurement of four four-wire PT1000s with a single constant current source without affecting the accuracy and stability; as shown in Figure c-2, the more measurement points, the more accurate the temperature control, and the analog-to-digital conversion chip used can provide 8-way differential input signals, which can measure the temperature of 8 temperature measurement points at the same time.

6. The high-precision temperature control circuit according to claim 1, characterized in that: The constant current source circuit includes a first operational amplifier U5, a second operational amplifier U6, a digital-to-analog converter U7, an eighth resistor R8, a ninth resistor R9, a first zero resistor R10, a first first resistor R11, and a first second resistor R12; The sixth pin of the digital-to-analog converter U7 is connected to the first end of the first zero resistor R10, the second end of the first zero resistor R10 is respectively connected to the non-inverting input end of the first operational amplifier U5 and the first end of the first resistor R11; the second end of the first resistor R11 is respectively connected to the inverting input end of the second operational amplifier U6 and the output end of the second operational amplifier U6; The inverting input terminal of the first operational amplifier U5 is respectively connected to the second end of the eighth resistor R8 and the first end of the ninth resistor R9, and the first end of the eighth resistor R8 is grounded; The output end of the first operational amplifier U5 is connected to the second end of the ninth resistor R9 and the first end of the second resistor R12 respectively, and the second ends of the first and second resistors R12 are connected to the non-inverting input end of the second operational amplifier U6.

7. The high-precision temperature control circuit according to claim 6, characterized in that: The digital-to-analog converter U7 outputs a programmable voltage value VOUT, which is input to the non-inverting input terminal of the differential op amp U5. The output terminal of the op amp U5 is connected to the precision resistor R12, which is connected to the non-inverting input terminal of the op amp U6. The op amp U6 builds a voltage follower, and the output terminal is connected to the REF terminal of the differential op amp U6. At this time: And R8=R9=R10=R11, then Among them, VOUT is the output terminal of the differential operational amplifier. Due to the low offset voltage, low gain error and integrated resistance of the differential operational amplifier U5, as well as the extremely high common-mode rejection ratio, it can output a high-precision voltage value; the operational amplifier U6 feeds back the voltage generated by IOUT flowing through the load to the REF terminal of the differential operational amplifier U5, so that the circuit can quickly establish and output a stable current source; the digital-to-analog converter U7 adopts a 20-bit model, and the size of the current source can be changed by changing the output accurate voltage of the digital-to-analog converter.

8. The high-precision temperature control circuit according to claim 1, characterized in that: In order to make the platinum resistance thermometer RTD and temperature have an approximately linear conversion relationship, the temperature range is divided into multiple intervals. The corresponding relationship between resistance and temperature in each interval is linear. The more intervals there are, the higher the accuracy. The resistance of the RTD is found out by an algorithm, and then the temperature is calculated by segmented interpolation. The temperature range is divided into multiple intervals, and the binary method is used to find the temperature interval in which the measured resistance value is located. The principle is to divide all temperature values ​​into half and take the middle value, compare the measured resistance value and the middle value, and then put them into the other half, and repeat the middle value comparison until the corresponding temperature interval is found; the temperature interval is selected as 1℃, that is, a calibration point is taken every 1℃, and the first-order linear equation fitted by the two calibration points, the measured resistance value is in a certain interval, and the current temperature value can be calculated; Using this algorithm requires the establishment of a resistance-temperature table.

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