Resistance gauge based on constant-temperature measurement environment

Abstract

The invention discloses a resistance gauge based on a constant-temperature measurement environment, and relates to the technical field of resistance gauges. The heating wire is wrapped and clung to the inner pipe wall of the metal pipe body through a high-temperature-resistant enameled wire; the thermistor is mounted through the metal tube body and is used for measuring the temperature of the metal tube body; the spiral thermal resistance wire extends into the metal tube body, and electrodes at the two ends of the spiral thermal resistance wire are connected through a thermal resistance wire lead; one end of the base is connected with a port of the metal pipe body; a plurality of wiring pins penetrate through the base, and respectively lead out the electrode of the heating wire, the electrode of the spiral thermal resistance wire and the lead of the thermistor; the vacuum gauge is used for controlling the temperature of the metal pipe body to be a preset temperature value by using a PID algorithm; the measuring module is also used for measuring voltage between electrodes at two ends of the spiral thermal resistance wire and calculating to obtain actual vacuum degree; through the arrangement of the heating wire, the internal temperature of the metal pipe body can be constant at a preset temperature value, so that the influence of the environment temperature on vacuum degree measurement is eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of resistance gauges, and more specifically, it relates to a resistance gauge based on a constant-temperature measurement environment. Background Art

[0002] A resistance gauge is a device used to measure vacuum degree and is widely applied in the field of vacuum technology. In existing traditional resistance gauges, the measured voltage of the thermal resistance wire often changes due to the change of ambient temperature, resulting in inaccurate measurement results. Summary of the Invention

[0003] The purpose of the present invention is to provide a resistance gauge based on a constant-temperature measurement environment to solve the problems existing in the above background art.

[0004] The above technical purpose of the present invention is achieved through the following technical solutions: In a first aspect, the present application provides a resistance gauge based on a constant-temperature measurement environment, including: A metal tube body; A heating wire, which is wrapped by a high-temperature resistant enameled wire and closely attached to the inner wall of the metal tube body; A thermistor, which is installed through the metal tube body and is used to measure the temperature of the metal tube body; A spiral thermal resistance wire, which extends into the metal tube body and does not contact the inner wall of the metal tube body. The electrodes at both ends of the spiral thermal resistance wire are connected by a thermal resistance wire lead; A base, one end of which is connected to the port of the metal tube body; Multiple wiring pins, which penetrate through the base and lead out the electrodes of the heating wire, the electrodes of the spiral thermal resistance wire, and the leads of the thermistor respectively; A vacuum gauge, which is used to control the temperature of the metal tube body to a preset temperature value by using the PID algorithm and controlling the energization time of the heating wire and receiving the temperature measurement feedback of the thermistor; and is also used to measure the voltage between the electrodes at both ends of the spiral thermal resistance wire and calculate the actual vacuum degree according to the voltage between the two electrodes.

[0005] The beneficial effect of the present invention is: In this solution, by energizing and heating the heating wire in the metal tube body to make its temperature higher than the temperature of the surrounding gas and the tube shell in the metal tube body, heat conduction caused by the thermal motion of gas molecules is generated between the heating wire and the tube shell; the problem that the thermal motion of gas molecules in the metal tube body and the heat conduction of the thermal resistance wire lead are affected by the change of ambient temperature is solved. By setting the heating wire, the internal temperature of the metal tube body can be kept constant at a preset temperature value, such as 45°C, so as to eliminate the influence of ambient temperature on the measurement of vacuum degree.

[0006] In this solution, for the measurement of the voltage of the thermal resistance wire, a constant temperature circuit is used for measurement; when the vacuum degree is different, the density of gas molecules is different, and the heat carried away by the molecular thermal motion of gas molecules is also different; the temperature of the thermal resistance wire is kept constant under different vacuum degrees. When the vacuum degree changes, the molecular thermal motion decreases, the current for the thermal resistance wire to be heated to maintain a constant temperature decreases, and the voltage across the thermal resistance wire decreases. Therefore, measuring the change in the voltage across the thermal resistance wire can reflect the change in the vacuum degree.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the above heating wire has a spiral structure.

[0009] The beneficial effect of adopting the above further solution is that the heating wire with a spiral structure can cover the inner wall of the metal tube body, making the heating inside the metal tube body more uniform.

[0010] Furthermore, the above thermistor is located in a hole opened at the port of the metal tube body, and the hole is filled with thermal conductive silicone grease.

[0011] The beneficial effect of adopting the above further solution is that it enables the thermistor to be in full contact with the metal tube body, facilitating more accurate measurement of the temperature of the metal tube body.

[0012] Furthermore, the above vacuum gauge includes a main control chip, a heating wire drive circuit, a thermistor temperature measurement circuit, and a PID constant temperature control module.

[0013] Furthermore, the above vacuum gauge further includes a vacuum degree display module for displaying the actual vacuum degree.

[0014] Furthermore, the model of the above main control chip is STM32F103VCT6.

[0015] Furthermore, the above thermistor temperature measurement circuit includes an instrumentation amplifier U1, an operational amplifier U2A, and an operational amplifier U2B, where: The third pin and the second pin of the instrumentation amplifier U1 are respectively connected to both ends of the resistor R7. The fourth pin of the instrumentation amplifier U1 is respectively connected to one end of the capacitor C1 and one end of the capacitor C3. The first pin of the instrumentation amplifier U1 is respectively connected to one end of the capacitor C5 and the other end of the capacitor C3. The other ends of the capacitor C1 and the capacitor C5 are both grounded. The fourth pin of the instrumentation amplifier U1 is also connected to one end of the resistor R4. The other end of the resistor R4 is respectively connected to one end of the resistor R3 and one end of the resistor R12. The other end of the resistor R3 forms the connection terminal A. The other end of the resistor R12 is connected to one end of the resistor R11. The first pin of the instrumentation amplifier U1 is also connected to one end of the resistor R9. The other end of the resistor R9 is connected to the other end of the resistor R11 and together form the connection terminal B. The connection terminal A and the connection terminal B are respectively connected to both ends of the thermistor. The third pin of the operational amplifier U2A is respectively connected to one end of the resistor R6 and one end of the capacitor C4. The other end of the resistor R6 is respectively connected to one end of the capacitor C2 and one end of the resistor R5. The other end of the resistor R5 is connected to the seventh pin of the instrumentation amplifier U1. The other end of the capacitor C2 is respectively connected to the second pin and the first pin of the operational amplifier U2A. The other end of the capacitor C4 is connected to the fourth pin of the operational amplifier U2A. The third pin of the operational amplifier U2B is respectively connected to one end of the resistor R10 and one end of the capacitor C6. The other end of the resistor R10 is connected to the first pin of the operational amplifier U2A. The other end of the capacitor C6 is connected to the fourth pin of the operational amplifier U2B. The second pin of the operational amplifier U2B is respectively connected to one end of the resistor R1 and one end of the resistor R2. The other end of the resistor R1 is grounded. The other end of the resistor R2 is connected to one end of the sliding rheostat RP1. The first pin of the operational amplifier U2B is connected to one end of the resistor R8. The other end of the resistor R8 is connected to the other end of the sliding rheostat RP1 and both are connected to the main control chip.

[0016] Furthermore, the above heating wire drive circuit includes an optocoupler transistor U3, a field effect transistor Q1, and a triode Q2, where: The base of the triode Q2 is respectively connected to one end of the resistor R15 and one end of the resistor R17. The other end of the resistor R15 forms the PWM signal receiving end connected to the main control chip. The other end of the resistor R17 is connected to the emitter of the triode Q2. The collector of the triode Q2 is connected to one end of the resistor R13. The second pin of the optocoupler transistor U3 is connected to the other end of the resistor R13. The first pin and the fourth pin of the optocoupler transistor U3 are respectively connected to one end of the capacitor C7 and one end of the capacitor C8. The other ends of the capacitor C7 and the capacitor C8 are both grounded. One end of resistor R14 and one end of resistor R16 are respectively connected to the gate of field effect transistor Q1. The other end of resistor R14 is connected to the 3rd pin of optocoupler transistor U3, and the other end of resistor R16 is connected to the source of field effect transistor Q1. The drain of field effect transistor Q1 is connected to the input end of diode D1, and the input end and output end of diode D1 respectively form connection end D and connection end C for connecting the two electrodes of the spiral thermal resistance wire.

[0017] Furthermore, the model of the instrumentation amplifier U1 is AD8226, the models of operational amplifiers U2A and U2B are OPA2188; the model of optocoupler transistor U3 is N-channel field effect transistor IRFP4568.

[0018] In a second aspect, the present application provides an application of a resistance gauge based on a constant temperature measurement environment in measuring vacuum degree as described in any one of the first aspects.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: In the present application, by energizing the heating wire inside the metal tube to heat it, so that its temperature is higher than the temperature of the surrounding gas and the tube shell of the metal tube, thus heat conduction caused by the thermal motion of gas molecules is generated between the heating wire and the tube shell; it solves the problem that the thermal motion of gas molecules inside the metal tube and the heat conduction of the lead wire of the thermal resistance wire are affected by the change of the ambient temperature. By setting the heating wire, the temperature inside the metal tube can be kept constant at a preset temperature value, such as 45 °C, thereby eliminating the influence of the ambient temperature on the vacuum degree measurement.

[0020] In the present application, the voltage of the thermal resistance wire is measured using a constant temperature circuit; when the vacuum degree is different, the gas molecular density is different, and the heat carried away by the molecular thermal motion of the gas molecules is also different; the temperature of the thermal resistance wire is kept constant under different vacuum degrees. When the vacuum degree changes, the molecular thermal motion decreases, the current for heating and maintaining the constant temperature of the thermal resistance wire decreases, and the voltage across the thermal resistance wire decreases. Therefore, measuring the change in the voltage across the thermal resistance wire can reflect the change in the vacuum degree; and the spiral heating wire can cover the inner wall of the metal tube, making the heating inside the metal tube more uniform. At the same time, the heat-conducting silicone grease filled in the holes can make the thermistor fully contact with the metal tube, facilitating more accurate measurement of the temperature of the metal tube. Description of the Drawings

[0021] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings: Figure 1 It is a schematic diagram of the distribution of the base and each wiring pin in the embodiment of the present invention; Figure 2 It is an exploded view of the resistance gauge in the embodiment of the present invention. Figure 3 It is a schematic diagram of the connection of part of the thermistor temperature measurement circuit in the embodiment of the present invention; Figure 4 It is a schematic diagram of the connection of another part of the thermistor temperature measurement circuit in the embodiment of the present invention; Figure 5 It is a schematic diagram of the connection of the heating wire drive circuit in the embodiment of the present invention.

[0022] Marks in the drawings and corresponding component names: 9. Base; 10. Wiring pin; 11. First electrode of the thermal resistance wire; 12. Spiral thermal resistance wire; 13. Second electrode of the thermal resistance wire; 14. First electrode of the heating wire; 15. Heating wire; 16. Inner tube wall; 17. Metal tube body; 18. Hole; 19. Thermistor; 20. First lead of the thermistor; 21. Second lead of the thermistor; 22. Second electrode of the heating wire; 23. Lead of the thermal resistance wire. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0027] In addition, when terms such as "horizontal", "vertical", "hanging" appear, it does not mean that the components are required to be absolutely horizontal or hanging, but they can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0028] In the description of the embodiments of the present invention, "a plurality of" represents at least two.

[0029] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, when terms such as "arranged", "installed", "connected", "coupled" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0030] Embodiment 1: In order to solve the problem that the current traditional resistance gauge often causes the change of the measured voltage of the thermal resistance wire due to the change of the ambient temperature, resulting in inaccurate measurement results, this embodiment provides a resistance gauge based on a constant temperature measurement environment, as Figure 1 and Figure 2 shown, including: A metal tube body 17; referring to Figure 2 , the metal tube body 17 can be formed in a cylindrical shape, and a cylindrical cavity is opened inside it, and the size of the cavity can correspond to the radial length of the heating wire 15; A heating wire 15, the heating wire 15 is wrapped by a high-temperature enameled wire and closely attached to the inner wall 16 of the metal tube body 17; preferably, the heating wire 15 is in a spiral structure, so that the heating wire 15 can cover the inner wall of the metal tube body 17, making the heating inside the metal tube body 17 more uniform; A thermistor 19, the thermistor 19 is installed through the metal tube body 17 and is used to measure the temperature of the metal tube body 17; preferably, the thermistor 19 is located in the hole 18 opened at the port of the metal tube body 17, and the hole 18 is filled with thermal conductive silicone grease, so that the thermistor 19 can be in full contact with the metal tube body 17, facilitating more accurate measurement of the temperature of the metal tube body 17; A spiral thermal resistance wire 12, the spiral thermal resistance wire 12 extends into the metal tube body 17 and does not contact the inner wall of the metal tube body 17, and the electrodes at both ends of the spiral thermal resistance wire 12 are connected by a thermal resistance wire lead 23; in Figure 2 , the electrodes at both ends of the spiral thermal resistance wire 12 are respectively represented as a thermal resistance wire first electrode 11 and a thermal resistance wire second electrode 13; Base 9, one end of the base 9 is connected to the port of the metal tube body 17; Multiple wiring pins 10, the multiple wiring pins 10 penetrate through the base 9, and lead out the electrodes of the heating wire 15, the electrodes of the spiral thermal resistance wire 12, and the leads of the thermistor 19 respectively; In Figure 2 it, the electrodes of the heating wire 15 are respectively denoted as the first electrode 14 of the heating wire and the second electrode 22 of the heating wire, and the leads of the thermistor 19 are respectively denoted as the first lead 20 of the thermistor and the second lead 21 of the thermistor; See Figure 1 , the first electrode 14 of the heating wire and the second electrode 22 of the heating wire of the heating wire 15 can be respectively led out through the wiring pins 10 numbered 4 and 1, the first lead 20 of the thermistor and the second lead 20 of the thermistor of the thermistor 19 can be respectively led out through the wiring pins 10 numbered 5 and 8, and the first electrode 11 of the thermal resistance wire and the second electrode 13 of the thermal resistance wire of the spiral thermal resistance wire 12 can be respectively led out through the wiring pins 10 numbered 2 and 3; Vacuum gauge, used to control the temperature of the metal tube body 17 to a preset temperature value by using the PID algorithm and controlling the energization time of the heating wire 15 and receiving the temperature measurement feedback of the thermistor 19; It is also used to measure the voltage between the two electrodes at both ends of the spiral thermal resistance wire 12, and calculate the actual vacuum degree according to the voltage between the two electrodes.

[0031] Among them, the preset temperature value can be 45 degrees. By adjusting the energization time and power-off time of the heating wire 15 through PWM, the temperature of the resistance metal tube body 17 is kept constant at 45 °C, ensuring that the ambient temperature measured inside the metal tube body 17 is 45 °C, which is higher than the working ambient temperature of the resistance gauge, eliminating the inaccurate measurement results caused by the change of the ambient temperature of the thermal resistance wire. It should be noted that the preset temperature value of 45 degrees is applicable to the scenario where the ambient temperature is lower than 45 °C.

[0032] Optionally, the above vacuum gauge includes a main control chip, a heating wire 15 drive circuit, a thermistor 19 temperature measurement circuit, and a PID constant temperature control module; Among them, the above vacuum gauge also includes a vacuum degree display module for displaying the actual vacuum degree; Specifically, the model of the above main control chip is STM32F103VCT6.

[0033] Among them, to keep the temperature inside the metal tube body 17 constant, it is necessary to control the heat generation of the heating wire 15. When the heating wire 15 is powered on, it generates heat, and the heat input to the wall of the metal tube body 17 is greater than the heat dissipated from the wall of the metal tube body 17, so the temperature inside the metal tube body 17 rises. When the power is cut off and heating stops, the heating wire no longer generates heat, but it still has residual heat and can still input heat to the wall of the metal tube body 17. If the temperature of the heating wire is already very high before the power is cut off, a large amount of heat will still be input to the wall of the metal tube body 17 for some time after the power is cut off, and the temperature inside the metal tube body 17 will still rise. However, after a period of time, the temperature of the heating wire itself decreases, and the heat input to the wall of the metal tube body 17 is less than the heat dissipated from the wall of the metal tube body 17, so the temperature inside the metal tube body 17 will decrease. Therefore, by adjusting the power-on time and power-off time, the heat generation of the heating wire and the heat dissipation of the metal tube body 17 can be controlled.

[0034] Specifically, the constant temperature value can be set to 45 °C. The actual temperature inside the metal tube body 17 is measured by the temperature measurement circuit of the thermistor 19. The main control chip MCU calculates the duty cycle of the output PWM signal by performing PID algorithm operation on the measured value and the set value, so that the temperature inside the metal tube body 17 is kept constant at 45 °C; then the vacuum degree is measured by the constant temperature measurement circuit of the thermal resistance wire. After the main control chip MCU processes and calculates the measured voltage value, the actual vacuum degree value is displayed by the display module.

[0035] The above PID algorithm is executed by the PID constant temperature control module. PID algorithm control is a control strategy based on three parameters: proportional (P), integral (I), and derivative (D), and is widely used in industrial process control; its basic principle is to compare the deviation between the system output value (temperature measurement feedback, obtained by measuring with the thermistor 19) and the expected value (preset temperature value, 45 degrees in this embodiment), and use proportional, integral, and derivative operations to adjust the control quantity, so as to eliminate the deviation and achieve the control target; it has the advantages of simple principle: the algorithm of PID control is simple and easy to implement; strong robustness: PID control has less dependence on the system model and has strong robustness and adaptability; wide application range: PID control is applicable to various types of control systems, especially widely used in industrial process control, etc., so it will not be elaborated here.

[0036] Optionally, the above temperature measurement circuit of the thermistor 19 includes an instrumentation amplifier U1, an operational amplifier U2A, and an operational amplifier U2B, as Figure 3 shown, where: The third pin and the second pin of the instrumentation amplifier U1 are respectively connected to both ends of the resistor R7. The fourth pin of the instrumentation amplifier U1 is respectively connected to one end of the capacitor C1 and one end of the capacitor C3. The first pin of the instrumentation amplifier U1 is respectively connected to one end of the capacitor C5 and the other end of the capacitor C3. The other ends of the capacitor C1 and the capacitor C5 are both grounded; the fourth pin of the instrumentation amplifier U1 is also connected to one end of the resistor R4. The other end of the resistor R4 is respectively connected to one end of the resistor R3 and one end of the resistor R12. The other end of the resistor R3 forms the connection terminal A, and the other end of the resistor R12 is connected to one end of the resistor R11; the first pin of the instrumentation amplifier U1 is also connected to one end of the resistor R9. The other end of the resistor R9 is connected to the other end of the resistor R11 and together form the connection terminal B. The connection terminal A and the connection terminal B are respectively connected to both ends of the thermistor 19.

[0037] See Figure 3 and Figure 4 , the third pin of the operational amplifier U2A is respectively connected to one end of the resistor R6 and one end of the capacitor C4. The other end of the resistor R6 is respectively connected to one end of the capacitor C2 and one end of the resistor R5. The other end of the resistor R5 is connected to the seventh pin of the instrumentation amplifier U1. The other end of the capacitor C2 is respectively connected to the second pin and the first pin of the operational amplifier U2A. The other end of the capacitor C4 is connected to the fourth pin of the operational amplifier U2A.

[0038] See Figure 3 and Figure 4 , the third pin of the operational amplifier U2B is respectively connected to one end of the resistor R10 and one end of the capacitor C6. The other end of the resistor R10 is connected to the first pin of the operational amplifier U2A. The other end of the capacitor C6 is connected to the fourth pin of the operational amplifier U2B; the second pin of the operational amplifier U2B is respectively connected to one end of the resistor R1 and one end of the resistor R2. The other end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to one end of the slide rheostat RP1; the first pin of the operational amplifier U2B is connected to one end of the resistor R8. The other end of the resistor R8 is connected to the other end of the slide rheostat RP1 and both are connected to the main control chip.

[0039] Among them, the thermistor 19 is connected to the connection terminal A, the connection terminal B and forms a Wheatstone bridge with R3, R11, and R12; when the temperature changes, the resistance value of the thermistor 19 will change and is not equal to the resistance value of R3. At this time, the bridge is in an unbalanced state, and a voltage difference will be generated between the two bridge arms. The generated voltage difference is amplified by the instrumentation amplifier AD8226 (U1). The signal is filtered by the second-order RC low-pass filter composed of R5, C2 and R6, C4, and after being amplified by the operational amplifier OPA2188 (U2), it is collected by the 12-bit ADC of the main control chip STM32F103VCT6 to calculate the actual temperature value.

[0040] Optionally, the above heating wire 15 driving circuit includes an optocoupler transistor U3, a field effect transistor Q1, and a triode Q2, as Figure 5 shown, where: The base of the triode Q2 is respectively connected to one end of the resistor R15 and one end of the resistor R17. The other end of the resistor R15 forms a connection to the PWM signal receiving end of the main control chip, and the other end of the resistor R17 is connected to the emitter of the triode Q2; the collector of the triode Q2 is connected to one end of the resistor R13.

[0041] See Figure 5 , the second pin of the optocoupler transistor U3 is connected to the other end of the resistor R13. The first pin and the fourth pin of the optocoupler transistor U3 are respectively connected to one end of the capacitor C7 and one end of the capacitor C8. The other ends of the capacitor C7 and the capacitor C8 are both grounded.

[0042] See Figure 5 , the gate of the field effect transistor Q1 is respectively connected to one end of the resistor R14 and one end of the resistor R16. The other end of the resistor R14 is connected to the third pin of the optocoupler transistor U3, and the other end of the resistor R16 is connected to the source of the field effect transistor Q1; the drain of the field effect transistor Q1 is connected to the input end of the diode D1, and the input end and the output end of the diode D1 respectively form connection ends D and C for connecting the two electrodes at both ends of the spiral heating resistor wire 12.

[0043] Among them, the heating wire 15 is connected to the connection end C and the connection end D. The main control chip STM32F103VCT6 outputs a PWM signal. When the PWM is at a high level, the NPN triode 3904 (Q2) conducts, the optocoupler transistor EL357NB (U3) conducts, and R2 and R4 perform series voltage division on 12V to obtain a voltage value greater than the conduction voltage of the N-channel field effect transistor IRFP4568 (Q1), causing Q1 to conduct and the heating wire 15 to heat. When the PWM is at a low level, the NPN triode 3904 (Q2) is cut off, the optocoupler transistor EL357NB (U3) is cut off, and the voltage between the gate and the source of the N-channel field effect transistor IRFP4568 (Q1) is 0V, which is less than the conduction voltage of 10V of the N-channel field effect transistor IRFP4568 (Q1), that is, Q1 is cut off and the heating wire 15 stops heating; the heating wire belongs to an inductive energy storage device, so a Schottky diode B340A (D1) is connected in parallel at both ends of it to be used as a freewheeling diode to protect the pre-stage circuit.

[0044] Specifically, the model of the above instrumentation amplifier U1 is AD8226, and the models of the operational amplifiers U2A and U2B are OPA2188; the model of the optocoupler transistor U3 is N-channel field effect transistor IRFP4568.

[0045] Example 2: The embodiments of the present application provide an application of a resistance gauge based on a constant-temperature measurement environment in measuring vacuum degree as described in any one of the embodiments 1.

[0046] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A resistance gauge based on a constant-temperature measurement environment, characterized in that, Comprising: A metal tube body; A heating wire, which is wrapped by a high-temperature resistant enameled wire and closely attached to the inner wall of the metal tube body; A thermistor, which is installed through the metal tube body and is used to measure the temperature of the metal tube body; A spiral thermal resistance wire, which extends into the metal tube body and does not contact the inner wall of the metal tube body. The electrodes at both ends of the spiral thermal resistance wire are connected by a thermal resistance wire lead; A base, one end of which is connected to the port of the metal tube body; Multiple wiring pins, which penetrate the base and lead out the electrodes of the heating wire, the electrodes of the spiral thermal resistance wire, and the leads of the thermistor respectively; A vacuum gauge, which is used to control the temperature of the metal tube body to a preset temperature value by using the PID algorithm, controlling the energization time of the heating wire, and receiving the temperature measurement feedback of the thermistor; it is also used to measure the voltage between the electrodes at both ends of the spiral thermal resistance wire and calculate the actual vacuum degree according to the voltage between the electrodes at both ends.

2. The resistance gauge based on a constant-temperature measurement environment according to claim 1, wherein The heating wire is of a spiral structure.

3. A resistance gauge based on a constant-temperature measurement environment according to claim 1, characterized in that, The thermistor is located in a hole opened at the port of the metal tube body, and the hole is filled with thermal conductive silicone grease.

4. A resistance gauge based on a constant-temperature measurement environment according to any one of claims 1-3, characterized in that The vacuum gauge includes a main control chip, a heating wire drive circuit, a thermistor temperature measurement circuit, and a PID constant temperature control module.

5. A resistance gauge based on a constant-temperature measurement environment according to claim 4, characterized in that, The vacuum gauge also includes a vacuum degree display module for displaying the actual vacuum degree.

6. The resistance gauge based on a constant-temperature measurement environment according to claim 4, wherein The model of the main control chip is STM32F103VCT6.

7. A resistance gauge based on a constant-temperature measurement environment according to claim 4, characterized in that The thermistor temperature measurement circuit includes an instrumentation amplifier U1, an operational amplifier U2A, and an operational amplifier U2B, where: The 3rd pin and the 2nd pin of the instrumentation amplifier U1 are respectively connected to both ends of a resistor R7. The 4th pin of the instrumentation amplifier U1 is respectively connected to one end of a capacitor C1 and one end of a capacitor C3. The 1st pin of the instrumentation amplifier U1 is respectively connected to one end of a capacitor C5 and the other end of the capacitor C3. The other ends of the capacitor C1 and the capacitor C5 are both grounded; the 4th pin of the instrumentation amplifier U1 is also connected to one end of a resistor R4. The other end of the resistor R4 is respectively connected to one end of a resistor R3 and one end of a resistor R12. The other end of the resistor R3 forms a connection end A, and the other end of the resistor R12 is connected to one end of a resistor R11; the 1st pin of the instrumentation amplifier U1 is also connected to one end of a resistor R9. The other end of the resistor R9 is connected to the other end of the resistor R11 and together form a connection end B. The connection end A and the connection end B are respectively connected to both ends of the thermistor; The 3rd pin of the operational amplifier U2A is respectively connected to one end of a resistor R6 and one end of a capacitor C4. The other end of the resistor R6 is respectively connected to one end of a capacitor C2 and one end of a resistor R5. The other end of the resistor R5 is connected to the 7th pin of the instrumentation amplifier U1. The other end of the capacitor C2 is respectively connected to the 2nd pin and the 1st pin of the operational amplifier U2A. The other end of the capacitor C4 is connected to the 4th pin of the operational amplifier U2A; The 3rd pin of the operational amplifier U2B is respectively connected to one end of a resistor R10 and one end of a capacitor C6. The other end of the resistor R10 is connected to the 1st pin of the operational amplifier U2A, and the other end of the capacitor C6 is connected to the 4th pin of the operational amplifier U2B. The 2nd pin of the operational amplifier U2B is respectively connected to one end of a resistor R1 and one end of a resistor R2. The other end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to one end of a slide rheostat RP1. The 1st pin of the operational amplifier U2B is connected to one end of a resistor R8, and the other end of the resistor R8 is connected to the other end of the slide rheostat RP1 and both are connected to the main control chip.

8. A resistance gauge based on a constant-temperature measurement environment according to claim 7, characterized in that The heating wire drive circuit includes an optocoupler transistor U3, a field effect transistor Q1, and a triode Q2, where: The base of the triode Q2 is respectively connected to one end of a resistor R15 and one end of a resistor R17. The other end of the resistor R15 forms a connection to the PWM signal receiving end of the main control chip, and the other end of the resistor R17 is connected to the emitter of the triode Q2. The collector of the triode Q2 is connected to one end of a resistor R13. The 2nd pin of the optocoupler transistor U3 is connected to the other end of the resistor R13. The 1st pin and the 4th pin of the optocoupler transistor U3 are respectively connected to one end of a capacitor C7 and one end of a capacitor C8. The other ends of the capacitor C7 and the capacitor C8 are both grounded. The gate of the field effect transistor Q1 is respectively connected to one end of a resistor R14 and one end of a resistor R16. The other end of the resistor R14 is connected to the 3rd pin of the optocoupler transistor U3, and the other end of the resistor R16 is connected to the source of the field effect transistor Q1. The drain of the field effect transistor Q1 is connected to the input end of a diode D1, and the input end and the output end of the diode D1 respectively form connection terminals D and C for connecting to the two end electrodes of the spiral thermal resistance wire.

9. A resistance gauge based on a constant-temperature measurement environment according to claim 8, characterized in that, The model of the instrumentation amplifier U1 is AD8226, and the models of the operational amplifier U2A and the operational amplifier U2B are OPA2188. The model of the optocoupler transistor U3 is the N-channel field effect transistor IRFP4568.

10. Application of a resistance gauge based on a constant temperature measurement environment in measuring vacuum degree as described in any one of claims 1 - 9.

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