A sensor and a flow controller

Abstract

The present application provides a sensor and a flow controller, wherein the sensor is connected to a fluid pipeline and is used to detect the flow value of a fluid in the fluid pipeline in real time; the sensor comprises: an upstream resistor, a downstream resistor, a constant current source control module, a constant temperature difference control module and a plurality of path switching modules; the downstream resistor is arranged downstream of the upstream resistor; the constant current source control module is configured to provide a stable current source in a constant current mode; the constant temperature difference control module is configured to control the temperature of the upstream resistor and the downstream resistor of the fluid pipeline in a constant temperature difference mode; one end of at least one path switching module is electrically connected to the first end of the upstream resistor of the fluid pipeline, and the other end is electrically connected to the output end of the constant current source control module. The sensor provided by the present application can solve the problem of simultaneously achieving high-precision and low-power flow measurement in a wide flow range.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductor process equipment, and in particular, relates to a sensor and a flow controller. Background Art

[0002] At present, thermal mass flow controller (MFC) is an instrument for measuring and controlling fluid flow, which is widely used in semiconductor manufacturing, biopharmaceuticals, environmental monitoring and other fields that require precise control of fluid flow. Its working principle is based on the heat change caused by the fluid passing through the sensor. The size of the fluid flow will cause an imbalance in the sensor temperature or power. By monitoring this change, the actual flow of the fluid can be calculated.

[0003] Existing flow sensors usually use one of the two working modes: constant power or constant temperature difference. However, these two modes have certain limitations in their respective application ranges. The constant power mode is suitable for high flow rate conditions, but the measurement accuracy is low and it is easy to overheat under low flow rate conditions. It is also sensitive to ambient temperature and takes too long to respond when the flow rate changes. The constant temperature difference mode is suitable for low flow rate conditions, but it is easy to saturate under high flow rate conditions, and it is easy to age due to long-term high temperature operation. Therefore, it is difficult for existing flow sensors to achieve high-precision and low-power flow measurement in a wide flow range. Utility Model Content

[0004] The purpose of the present application is to provide a sensor and a flow controller, aiming to solve the problem in the prior art that it is difficult to achieve high-precision and low-power flow measurement in a wide flow range.

[0005] The first aspect of the present application provides a sensor, which is connected to a fluid pipeline and is used to detect the flow value of the fluid in the fluid pipeline in real time; the sensor includes: an upstream resistor, a downstream resistor, a constant current source control module, a constant temperature difference control module and multiple path switching modules; the downstream resistor is arranged downstream of the upstream resistor.

[0006] The constant current source control module is configured to provide a stable current source in a constant current mode; the constant temperature difference control module is configured to control the temperature of the upstream resistor and the downstream resistor of the fluid pipeline in a constant temperature difference mode; one end of at least one path switching module is electrically connected to the first end of the upstream resistor of the fluid pipeline, and the other end is electrically connected to the output end of the constant current source control module; one end of at least one path switching module is electrically connected to the first end of the downstream resistor of the fluid pipeline, and the other end is electrically connected to the output end of the constant temperature difference control module; one end of at least one path switching module is electrically connected to the second end of the upstream resistor, and the other end is electrically connected to the first end of the downstream resistor.

[0007] Based on the above scheme, the present application provides a sensor, which can measure the flow rate of the fluid pipeline in real time and feed back the flow rate value to the main control circuit; the main control circuit determines whether the fluid in the fluid pipeline is in a high-speed or low-speed state according to the detected flow rate value and the size of the preset range. When the flow rate exceeds the preset range, that is, it is in a high flow rate state at this time, the sensor works in a constant current mode; at this time, the path switching module is connected to the constant current source control module, and the power is supplied by the constant current source control module, so that the current of the sensor circuit is constant, and the power consumption will be reduced when the resistance is constant. When the flow rate does not exceed the preset range, that is, it is in a low flow rate state at this time, the sensor works in a constant temperature difference mode; at this time, the path switching module is connected to the constant temperature difference control module, and the temperature difference between the upstream resistor and the downstream resistor and the ambient temperature can be controlled by the constant temperature difference control module to be a constant value, which can further provide higher monitoring and control accuracy. That is to say, by adopting different working modes at different flow rates, high-precision flow measurement can be achieved in a wide flow range.

[0008] In some embodiments of the present application, the plurality of path switching modules include: a first path switching module, a second path switching module, and a third path switching module.

[0009] The first end of the first path switching module is electrically connected to the first end of the upstream resistor of the fluid pipeline, the second end of the first path switching module is electrically connected to the output end of the constant current source control module; the third end of the first path switching module is electrically connected to the output end of the constant temperature difference control module.

[0010] The first end of the second path switching module is electrically connected to the second end of the upstream resistor of the fluid pipeline, and is also electrically connected to the input end of the constant current source control module; the second end of the second path switching module is electrically connected to the first end of the downstream resistor; the third end of the second path switching module is electrically connected to the ground end.

[0011] A first end of the third passage switching module is electrically connected to a first end of a downstream resistor of the fluid pipeline, and a second end of the third passage switching module is electrically connected to an output end of the constant temperature difference control module.

[0012] The first path switching module is configured to select the power supply mode for the upstream resistor of the fluid pipeline; the second path switching module is configured to select the connection mode between the upstream resistor and the downstream resistor of the fluid pipeline; the second path switching module is configured to select the power supply mode for the downstream resistor of the fluid pipeline.

[0013] According to the above technical means, in the present application, the power supply mode for the upstream resistor of the fluid pipeline can be selected through the first path switching module, which can be powered by the current source of the constant current source control module or the voltage source of the constant temperature difference control module; the second path switching module is used to select one end of the upstream resistor to be grounded or connected in series with the downstream resistor; the third path switching module is used to select the power supply mode for the downstream resistor, which can be connected in series with the upstream resistor or powered by the voltage source of the constant temperature difference control module.

[0014] In some embodiments of the present application, the upstream resistance of the fluid pipeline is the upstream resistance, and the downstream resistance of the fluid pipeline is the downstream resistance.

[0015] In some embodiments, the constant temperature difference control module includes: a first bridge circuit, a second bridge circuit, a first operation circuit, and a first signal adjustment circuit.

[0016] The first end of the first bridge circuit is electrically connected to the third end of the first path switching module; the second end of the first bridge circuit is electrically connected to the ground end; the first end of the second bridge circuit is electrically connected to the second end of the third path switching module; the second end of the second bridge circuit is electrically connected to the ground end.

[0017] The first end of the first operation circuit is electrically connected to the third end of the first bridge circuit; the second end of the first operation circuit is electrically connected to the third end of the second bridge circuit; the first end of the first signal adjustment circuit is electrically connected to the third end of the first operation circuit; the second end of the first signal adjustment circuit is electrically connected to the main control circuit.

[0018] The first bridge circuit is configured to output a voltage signal of an upstream resistor and transmit it to a first operational circuit; the second bridge circuit is configured to output a voltage signal of a downstream resistor and transmit it to the first operational circuit; the first operational circuit is configured to calculate a difference between a voltage signal of an upstream resistor and a voltage signal of a downstream resistor.

[0019] According to the above technical means, the constant temperature difference control module in the present application switches the power supply of the upstream resistor and the downstream resistor to independent bridges in the module respectively through the first path switching module and the third path switching module, and the second path switching module grounds the other end of the upstream resistor. Through the feedback mechanism of the first bridge circuit and the second bridge circuit, the temperature of the upstream resistor and the downstream resistor can be kept independently controlled and constant.

[0020] In some embodiments of the present application, the first bridge circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first transistor, and a first operational amplifier.

[0021] The control end of the first transistor is electrically connected to the output end of the first operational amplifier, the first end of the first transistor is electrically connected to the first end of the fourth resistor, the second end of the first transistor is electrically connected to the second end of the fourth resistor, and is also electrically connected to the first end of the first resistor, the first end of the third resistor, and the third end of the first bridge circuit.

[0022] The first input terminal of the first operational amplifier is electrically connected to the second end of the first resistor, and is also electrically connected to the first end of the second resistor. The second end of the second resistor is electrically connected to the second end of the first bridge circuit. The second input terminal of the first operational amplifier is electrically connected to the second end of the third resistor, and is also electrically connected to the first end of the first bridge circuit.

[0023] In some embodiments of the present application, the second bridge circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second transistor, and a second operational amplifier.

[0024] The control end of the second transistor is electrically connected to the output end of the second operational amplifier, the first end of the second transistor is electrically connected to the first end of the eighth resistor, the second end of the second transistor is electrically connected to the second end of the eighth resistor, and is also electrically connected to the first end of the fifth resistor, the first end of the seventh resistor, and the third end of the second bridge circuit.

[0025] The first input terminal of the second operational amplifier is electrically connected to the second end of the fifth resistor, and is also electrically connected to the first end of the sixth resistor. The second end of the sixth resistor is electrically connected to the second end of the second bridge circuit; the second input terminal of the second operational amplifier is electrically connected to the second end of the seventh resistor, and is also electrically connected to the first end of the second bridge circuit.

[0026] In some embodiments of the present application, the first operational circuit includes: an instrumentation amplifier and a ninth resistor, the first input terminal of the instrumentation amplifier is electrically connected to the first terminal of the first operational circuit, the second input terminal of the instrumentation amplifier is electrically connected to the second terminal of the first operational circuit; the output terminal of the instrumentation amplifier is electrically connected to the output terminal of the first operational circuit.

[0027] A first end of the ninth resistor is electrically connected to the third input end of the instrument amplifier, and a second end of the ninth resistor is electrically connected to the fourth input end of the instrument amplifier.

[0028] In some embodiments of the present application, the constant current source control module includes: a constant current source, an adjustable resistor, a third bridge circuit, a second operation circuit and a second signal adjustment circuit.

[0029] The first end of the adjustable resistor is electrically connected to the output end of the constant current source, and is also electrically connected to the second end of the first path switching module, and the second end of the adjustable resistor is electrically connected to the main control circuit; the first end of the third bridge circuit is electrically connected to the first end of the adjustable resistor, and the second end of the third bridge circuit is electrically connected to the ground end.

[0030] The first end of the second operation circuit is electrically connected to the third end of the third bridge circuit, and the second end of the second operation circuit is electrically connected to the first end of the second path switching module; the first end of the second signal adjustment circuit is electrically connected to the third end of the second operation circuit, and the second end of the second signal adjustment circuit is electrically connected to the main control circuit.

[0031] According to the above technical means, the constant current source control module in the present application connects the upstream resistor and the downstream resistor in series through the second path switching module and the third path switching module. The first path switching module switches the power supply of the upstream resistor to the constant current source control module. The current source provides a stable current. When the fluid flows through the sensor circuit, the flow rate change is reflected by the temperature change on the upstream resistor.

[0032] In some embodiments of the present application, the third bridge circuit includes: a tenth resistor and an eleventh resistor; the first end of the tenth resistor is electrically connected to the first end of the third bridge circuit, the second end of the tenth resistor is electrically connected to the first end of the eleventh resistor, and is also electrically connected to the third end of the third bridge circuit; the second end of the eleventh resistor is electrically connected to the second end of the third bridge circuit.

[0033] According to the above technical means, the ratio of the resistance values ​​of the tenth resistor and the eleventh resistor in the present application is a fixed value, and the output voltage signal is transmitted to the second signal adjustment circuit through the second operation circuit, and then transmitted to the main control circuit through the second adjustment circuit, so as to calculate the flow rate.

[0034] The second aspect of the present application provides a flow controller, which includes: a sensor, a main control circuit and a valve. The main control circuit is electrically connected to the output end of the sensor; multiple control ends of the main control circuit are electrically connected to the control ends of the multiple path switching modules; the control end of the valve is electrically connected to the second end of the main control circuit; the valve is arranged at the outlet of the fluid pipeline, and the valve is configured to control the on-off of the fluid pipeline; the main control circuit is configured to switch the constant current source control module or the constant temperature difference control module to work according to the flow value detected by the sensor.

[0035] In some embodiments of the present application, the main control circuit includes: an analog front-end circuit, an analog-to-digital conversion circuit, a main control chip, a digital-to-analog conversion circuit and a valve drive circuit.

[0036] The input end of the analog-to-digital conversion circuit is electrically connected to the output end of the analog front-end circuit, and the output end of the analog-to-digital conversion circuit is electrically connected to the input end of the main control chip; the input end of the digital-to-analog conversion circuit is electrically connected to the output end of the main control chip, and the output end of the digital-to-analog conversion circuit is electrically connected to the input end of the valve drive circuit.

[0037] The input end of the analog front-end circuit is electrically connected to the first end of the main control circuit, and the output end of the valve drive circuit is electrically connected to the second end of the main control circuit; the analog front-end circuit is configured to further process the output signal of the sensor circuit to obtain a first analog signal, and transmit the first analog signal to the analog-to-digital conversion circuit.

[0038] The valve driving circuit is configured to control the opening of the valve to adjust the fluid flow.

[0039] Based on the above scheme, the present application provides a flow controller, which measures the flow size of the fluid pipeline in real time through a sensor circuit, and feeds back the flow value to the main control circuit; the main control circuit determines whether the fluid in the fluid pipeline is in a high-speed or low-speed state according to the detected flow value and the size of the preset range. When the flow exceeds the preset range, that is, it is in a high flow rate state at this time, the flow controller works in a constant current mode; at this time, the path switching module is connected to the constant current source control module, and the power is supplied by the constant current source control module, so that the current of the sensor circuit is constant, and the power consumption will be reduced when the resistance is constant. When the flow does not exceed the preset range, that is, it is in a low flow rate state at this time, the flow controller works in a constant temperature difference mode; at this time, the path switching module is connected to the constant temperature difference control module, and the temperature difference between the upstream resistor and the downstream resistor and the ambient temperature can be controlled by the constant temperature difference control module to be a constant value, which can further provide higher monitoring and control accuracy. That is to say, by adopting different working modes at different flow rates, high-precision flow measurement can be achieved in a wide flow range. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a structural block diagram of a sensor provided in some embodiments of the present application;

[0041] Figure 2 is a specific circuit diagram of a constant temperature difference control module provided in some embodiments of the present application;

[0042] Figure 3 is a specific circuit diagram of a constant current source control module provided in some embodiments of the present application;

[0043] Figure 4 is a schematic diagram of a flow controller provided in some embodiments of the present application;

[0044] Figure 5 This is a structural block diagram of a system in which a flow controller is located, provided in some embodiments of the present application. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0046] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0047] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply 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 understood as a limitation on the present application.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] Existing flow sensing technologies are generally based on the application of King's Law, which relates the fluid flow rate v to the temperature T or power P of the sensing element. The relationship can be written as the following equation (1):

[0050] P=I 2 R=(T-Ta)(A+B*V n ) (1).

[0051] Where I is the input current of the sensor element, R is the resistance of the sensor element, Ta is the ambient temperature, A, B, and n are coefficients determined by the physical thermal model of the sensor and can be determined by simulation or calibration. n is usually taken as 0.5.

[0052] From the above equation, we can see that the process of calculating flow rate depends on the ambient temperature Ta, so in practical applications, the industry usually uses two sensor elements placed upstream and downstream of the flow channel, and avoids the ambient temperature variable from participating in the calculation by using the temperature or power difference on both sides. These are also the two commonly used working modes of flow sensors, namely constant power mode and constant temperature difference mode.

[0053] In constant power mode, v is calculated by measuring the temperature difference ΔT, which is mainly suitable for scenarios with large flow rates. The main defects of this method are: the temperature rise is high in zero or small flow scenarios, which may cause thermal shock to the system; it is sensitive to ambient temperature; and because the heating power is constant, the response time is slow when the flow changes greatly.

[0054] In the constant temperature difference mode, v is calculated by measuring the power difference ΔP. The main defects are: more power consumption is required to maintain the constant temperature difference state in large flow scenarios, and it is easy to reach saturation due to the limitation of the system power supply design; the operating temperature is usually relatively high, and long-term high-temperature operation can easily cause sensor aging and affect output accuracy.

[0055] Based on this, an embodiment of the present application provides a sensor, such as Figure 1 As shown, the sensor 100 comprises: an upstream resistor Ru, a downstream resistor Rd, a constant current source control module 1, a constant temperature difference control module 2 and a plurality of path switching modules 3. The sensor is connected to the fluid pipeline and is used to detect the flow value of the fluid in the fluid pipeline in real time.

[0056] It can be understood that the fluid pipeline can be a main pipeline or a bypass pipeline.

[0057] The upstream resistor Ru and the downstream resistor Rd are windings wound on the fluid pipeline, and the downstream resistor is arranged downstream of the upstream resistor, that is, the positions of the two are relative.

[0058] The constant current source 11 control module 1 is configured to provide a stable current source in a constant current mode; the constant temperature difference control module 2 is configured to control the temperature of the upstream resistor Ru and the downstream resistor Rd of the fluid pipeline in a constant temperature difference mode.

[0059] One end of at least one path switching module 3 is electrically connected to the first end of the upstream resistor Ru of the fluid pipeline, and the other end is electrically connected to the output end of the constant current source 11 control module 1.

[0060] One end of at least one passage switching module 3 is electrically connected to the first end of the downstream resistor Rd of the fluid pipeline, and the other end is electrically connected to the output end of the constant temperature difference control module 2 .

[0061] One end of at least one path switching module 3 is electrically connected to the second end of the upstream resistor Ru, and the other end is electrically connected to the first end of the downstream resistor Rd.

[0062] The path switching module is equivalent to a switch, and different working modes of the sensor can be controlled by controlling different path switching modules. That is, through multiple path switching modules, the sensor can be in different working modes, so that the constant current source control module 1 or the constant temperature difference control module 2 is in working state.

[0063] Reference Figure 1 It can be seen that the sensor itself only has the function of detection, so it needs to be used in conjunction with the main control circuit. First, the main control circuit needs to power the sensor, and the sensor will also transmit the detected signal to the main control circuit.

[0064] In the constant current mode, one end of at least one path switching module 3 is electrically connected to the first end of the upstream resistor Ru of the fluid pipeline, and the other end is electrically connected to the output end of the constant current source 11 control module 1, that is, the path switching module is required to make the constant current source control module connected to the upstream resistor Ru; at the same time, one end of at least one path switching module 3 is electrically connected to the second end of the upstream resistor Ru, and the other end is electrically connected to the first end of the downstream resistor Rd, that is, the path switching module is required to make the downstream resistor Rd connected to the upstream resistor Ru.

[0065] At this time, the upstream resistor Ru and the downstream resistor Rd are connected in series, and the power supply is switched to the constant current source in the constant current source control module. When the fluid flows through the sensor, the temperature change on the resistor reflects the change in flow rate, that is, the flow rate is reflected by ΔT=Td-Tu. Td refers to the temperature of the downstream resistor, and Tu refers to the temperature of the upstream resistor.

[0066] Among them, the output voltage of the constant current source in the constant current source control module is Vh, so the output voltage Vout can be detected. From the characteristics of the relationship between resistance and temperature, it can be seen that the greater the temperature difference, the greater the difference between Rd-Ru, and the greater the output voltage Vout, so that the flow change can be reflected through Vout.

[0067] Similarly, in the constant temperature difference mode, one end of at least one path switching module 3 is electrically connected to the first end of the downstream resistor Rd of the fluid pipeline, and the other end is electrically connected to the output end of the constant temperature difference control module 2, that is, the path switching module is required to connect the constant temperature difference control module to the downstream resistor Rd; at the same time, one end of at least one path switching module 3 is electrically connected to the second end of the upstream resistor Ru, and the other end is electrically connected to the first end of the downstream resistor Rd, so that the second end of the upstream resistor is grounded.

[0068] At this time, the upstream resistor Ru is powered by the constant current source control module, and the downstream resistor Rd is powered by the constant temperature difference control module. When the fluid flows through the sensor, the greater the flow rate, the greater the difference in the supply voltage of the upstream and downstream bridges, so Vout can be used to calculate the fluid flow rate, and Vu and Vd can be used for temperature correction.

[0069] Vu refers to the voltage of the upstream resistor, and Vd refers to the voltage of the downstream resistor. Since the upstream resistor and the downstream resistor are powered separately, the temperature difference between the upstream resistor and the temperature of the downstream resistor and the ambient temperature can be kept constant through the constant temperature difference control module and the constant current source control module, that is, T-Ta is kept constant. The flow rate v of the fluid can be obtained through the voltage of the upstream resistor and the downstream resistor.

[0070] When the flow rate in the pipeline is small, the constant temperature difference mode is used, which provides higher monitoring and control accuracy; when the flow rate is large, the constant current mode is used. The constant current mode maintains the current of the sensor element constant, which consumes less power than the constant temperature difference mode. The main control circuit switches between different modes, allowing the sensor to achieve high-precision flow measurement in a wide flow range.

[0071] In some embodiments, when used to monitor long-term stable gases, the sensor can be selectively switched to constant current mode to avoid long-term high-temperature heating of the sensor resulting in aging and performance degradation.

[0072] Based on the above scheme, some embodiments of the present application provide a sensor 100, which can measure the flow rate of the fluid pipeline in real time and feed back the flow rate value to the main control circuit 110; the main control circuit 110 determines whether the fluid in the fluid pipeline is in a high-speed or low-speed state according to the detected flow rate value and the size of the preset range. When the flow rate exceeds the preset range, that is, it is in a high flow rate state at this time, the sensor 100 works in a constant current mode; at this time, the path switching module 3 is connected to the constant current source 11 control module 1, and the constant current source 11 control module 1 is powered, so that the current of the sensor 100 circuit is constant, and the power consumption will be reduced when the resistance is constant. When the flow rate does not exceed the preset range, that is, it is in a low flow rate state at this time, the sensor 100 works in a constant temperature difference mode; at this time, the path switching module 3 is connected to the constant temperature difference control module 2, and the temperature difference between the upstream resistor Ru and the downstream resistor Rd and the ambient temperature can be controlled by the constant temperature difference control module 2 to be a constant value, which can further provide higher monitoring and control accuracy. That is to say, by adopting different working modes at different flow rates, high-precision flow measurement can be achieved in a wide flow range.

[0073] like Figure 1 As shown, in some embodiments, the plurality of path switching modules 3 include: a first path switching module 31 , a second path switching module 32 and a third path switching module 33 .

[0074] The first end of the first path switching module 31 is electrically connected to the first end of the upstream resistor Ru of the fluid pipeline, the second end of the first path switching module 31 is electrically connected to the output end of the constant current source 11 control module 1; the third end of the first path switching module 31 is electrically connected to the output end of the constant temperature difference control module 2.

[0075] The first end of the second path switching module 32 is electrically connected to the second end of the upstream resistor Ru of the fluid pipeline, and is also electrically connected to the input end of the constant current source 11 control module 1; the second end of the second path switching module 32 is electrically connected to the first end of the downstream resistor Rd; the third end of the second path switching module 32 is electrically connected to the ground end.

[0076] A first end of the third path switching module 33 is electrically connected to a first end of a downstream resistor Rd of the fluid pipeline, and a second end of the third path switching module 33 is electrically connected to an output end of the constant temperature difference control module 2 .

[0077] The first path switching module 31 is configured to select the power supply mode for the upstream resistor Ru of the fluid pipeline; the second path switching module 32 is configured to select the connection mode between the upstream resistor Ru and the downstream resistor Rd of the fluid pipeline; the second path switching module 32 is configured to select the power supply mode for the downstream resistor Rd of the fluid pipeline.

[0078] According to the above-mentioned technical means, in the present application, the first path switching module 31 can be used to select the power supply mode for the upstream resistor Ru of the fluid pipeline, which can be powered by the current source of the constant current source 11 control module 1, or by the voltage source of the constant temperature difference control module 2; the second path switching module 32 is used to select one end of the upstream resistor Ru to be grounded or connected in series with the downstream resistor Rd; the third path switching module 33 is used to select the power supply mode of the downstream resistor Rd, which can be connected in series with the upstream resistor Ru, or powered by the voltage source of the constant temperature difference control module 2.

[0079] like Figure 2 As shown, the constant temperature difference control module 2 includes: a first bridge circuit 21 , a second bridge circuit 22 , a first operation circuit 23 and a first signal adjustment circuit 24 .

[0080] The first end of the first bridge circuit 21 is electrically connected to the third end of the first path switching module 31; the second end of the first bridge circuit 21 is electrically connected to the ground; the first end of the second bridge circuit 22 is electrically connected to the second end of the third path switching module 33; the second end of the second bridge circuit 22 is electrically connected to the ground.

[0081] The first end of the first operation circuit 23 is electrically connected to the third end of the first bridge circuit 21; the second end of the first operation circuit 23 is electrically connected to the third end of the second bridge circuit 22; the first end of the first signal adjustment circuit 24 is electrically connected to the third end of the first operation circuit 23; the second end of the first signal adjustment circuit 24 is electrically connected to the main control circuit 110.

[0082] The first bridge circuit 21 is configured to output the voltage signal of the upstream resistor Ru and transmit it to the first operation circuit 23; the second bridge circuit 22 is configured to output the voltage signal of the downstream resistor Rd and transmit it to the first operation circuit 23; the first operation circuit 23 is configured to calculate the difference between the voltage signal of the upstream resistor Ru and the voltage signal of the downstream resistor Rd.

[0083] The first signal conditioning circuit 24 is configured to process the analog signals Vu, Vd and Vout and shape the output signals.

[0084] According to the above technical means, the constant temperature difference control module 2 in the present application switches the power supply of the upstream resistor Ru and the downstream resistor Rd to independent bridges in the module respectively through the first path switching module 31 and the third path switching module 33, and the second path switching module 32 grounds the other end of the upstream resistor Ru. Through the feedback mechanism of the first bridge circuit 21 and the second bridge circuit 22, the temperature of the upstream resistor Ru and the downstream resistor Rd can be kept independently controlled and constant.

[0085] like Figure 2 As shown, in some embodiments, the first bridge circuit 21 includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first transistor Q1, and a first operational amplifier OPA1.

[0086] The control end of the first transistor Q1 is electrically connected to the output end of the first operational amplifier OPA1, the first end of the first transistor Q1 is electrically connected to the first end of the fourth resistor R4, the second end of the first transistor Q1 is electrically connected to the second end of the fourth resistor R4, and is also electrically connected to the first end of the first resistor R1, the first end of the third resistor R3, and the third end of the first bridge circuit 21.

[0087] The first input terminal of the first operational amplifier OPA1 is electrically connected to the second end of the first resistor R1, and is also electrically connected to the first end of the second resistor R2. The second end of the second resistor R2 is electrically connected to the second end of the first bridge circuit 21. The second input terminal of the first operational amplifier OPA1 is electrically connected to the second end of the third resistor R3, and is also electrically connected to the first end of the first bridge circuit 21.

[0088] According to the above technical means, the voltage difference output by the first bridge circuit 21 in the present application controls the power supply voltage Vu of the first bridge circuit 21 through an NPN transistor after passing through the first operational amplifier OPA1, and finally makes R1 / R2=R3 / Ru, achieving a constant temperature difference state.

[0089] In some embodiments, the second bridge circuit 22 includes: a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second transistor Q2, and a second operational amplifier OPA2.

[0090] The control end of the second transistor Q2 is electrically connected to the output end of the second operational amplifier OPA2, the first end of the second transistor Q2 is electrically connected to the first end of the eighth resistor R8, the second end of the second transistor Q2 is electrically connected to the second end of the eighth resistor R8, and is also electrically connected to the first end of the fifth resistor R5, the first end of the seventh resistor R7, and the third end of the second bridge circuit 22.

[0091] The first input terminal of the second operational amplifier OPA2 is electrically connected to the second end of the fifth resistor R5, and is also electrically connected to the first end of the sixth resistor R6. The second end of the sixth resistor R6 is electrically connected to the second end of the second bridge circuit 22; the second input terminal of the second operational amplifier OPA2 is electrically connected to the second end of the seventh resistor R7, and is also electrically connected to the first end of the second bridge circuit 22.

[0092] According to the above technical means, the voltage difference output by the second bridge circuit 22 in the present application controls the power supply voltage Vd of the first bridge circuit 21 through an NPN transistor after passing through the second operational amplifier OPA2, and finally makes R5 / R6=R7 / Rd, achieving a constant temperature difference state.

[0093] In some embodiments, the first transistor Q1 and the second transistor Q2 are triodes.

[0094] It should be noted that in order to prevent the first operational amplifier and the second operational amplifier from outputting 0V, causing the first transistor Q1 and the second transistor Q2 to be in the cut-off state, the fourth resistor R4 is connected to the first end and the second end of the first transistor Q1, and the eighth resistor R8 is connected to the first end and the second end of the second transistor Q2. In this way, an initial voltage can be provided for the first bridge circuit and the second bridge circuit to prevent the first transistor Q1 and the second transistor Q2 from being cut off.

[0095] In some embodiments, the first operational circuit 23 includes: an instrumentation amplifier and a ninth resistor R9, the first input terminal of the instrumentation amplifier is electrically connected to the first terminal of the first operational circuit 23, the second input terminal of the instrumentation amplifier is electrically connected to the second terminal of the first operational circuit 23; the output terminal of the instrumentation amplifier is electrically connected to the output terminal of the first operational circuit 23.

[0096] A first end of the ninth resistor R9 is electrically connected to the third input end of the instrument amplifier, and a second end of the ninth resistor R9 is electrically connected to the fourth input end of the instrument amplifier.

[0097] According to the above technical means, the voltage signals Vu and Vd of the upstream and downstream resistors Rd in the present application calculate their difference through an instrument amplifier INA, the ninth resistor R9 is used to adjust the gain of the instrument amplifier, and the output signal Vout is a flow signal, which is transmitted back to the main control circuit 110 together with the voltage signals Vu and Vd through the signal adjustment circuit.

[0098] like Figure 3 As shown, the constant current source control module 1 includes: a constant current source 11 , an adjustable resistor Rset, a third bridge circuit 13 , a second operation circuit 14 and a second signal adjustment circuit 15 .

[0099] The first end of the adjustable resistor Rset is electrically connected to the output end of the constant current source 11, and is also electrically connected to the second end of the first path switching module 31. The second end of the adjustable resistor Rset is electrically connected to the main control circuit 110; the first end of the third bridge circuit 13 is electrically connected to the first end of the adjustable resistor Rset, and the second end of the third bridge circuit 13 is electrically connected to the ground end.

[0100] A first end of the second operation circuit 14 is electrically connected to a third end of the third bridge circuit 13, and a second end of the second operation circuit 14 is electrically connected to a first end of the second path switching module 32; a first end of the second signal adjustment circuit 15 is electrically connected to a third end of the second operation circuit 14, and a second end of the second signal adjustment circuit 15 is electrically connected to the main control circuit 110.

[0101] The second signal conditioning circuit 15 is configured to process the analog signals Vh and Vout and shape the output signal.

[0102] In some embodiments, the constant current source control module 1 further includes: a current limiting resistor RL, a first end of the current limiting resistor RL is electrically connected to the output end of the constant current source 11, and a second end of the current limiting resistor RL is electrically connected to the first end of the adjustable resistor Rset.

[0103] In the present application, the constant current source control module 1 connects the upstream resistor Ru and the downstream resistor Rd in series through the first path switching module 31 and the second path switching module 32. The first path switching module 31 switches the power supply of the upstream resistor Ru to the constant current source control module 1. The current source provides a stable current. When the fluid flows through the sensor 100 circuit, the flow rate change is reflected by the temperature change on the upstream resistor Ru.

[0104] like Figure 3 As shown, the third bridge circuit 13 includes: a tenth resistor R10 and an eleventh resistor R11.

[0105] The first end of the tenth resistor R10 is electrically connected to the first end of the third bridge circuit 13 , the second end of the tenth resistor R10 is electrically connected to the first end of the eleventh resistor R11 , and is also electrically connected to the third end of the third bridge circuit 13 ; the second end of the eleventh resistor R11 is electrically connected to the second end of the third bridge circuit 13 .

[0106] Among them, in some embodiments, the resistance ratio of the tenth resistor R10 and the eleventh resistor R11 in the present application is a fixed value, and the output voltage signal is transmitted to the second signal adjustment circuit 15 through the second operation circuit 14, and then transmitted to the main control circuit 110 through the second adjustment circuit, so as to calculate the flow rate.

[0107] Among them, the upstream resistor Ru and the downstream resistor Rd are in the initial state of no flow, ideally Ru=Rd, and practically approximate. At this time, if the resistance values ​​of the tenth resistor R10 and the eleventh resistor R11 are the same, that is, R10=R11; the output voltages of both arms of the bridge are Vh / 2, so that Vout=0V.

[0108] like Figure 4 As shown, some embodiments of the present application provide a flow controller, wherein the flow controller 200 includes: a sensor 100 , a main control circuit 110 and a valve 210 .

[0109] The main control circuit 110 is electrically connected to the output end of the sensor 100 ; multiple control ends of the main control circuit 110 are electrically connected to control ends of multiple path switching modules 3 (not shown in the figure); the control end of the valve 210 is electrically connected to the second end of the main control circuit 110 .

[0110] The valve 210 is arranged at the outlet of the fluid pipeline, and the valve is configured to control the on-off of the fluid pipeline; the main control circuit 110 is configured to switch the operation of the constant current source control module 1 or the constant temperature difference control module 2 according to the flow value detected by the sensor 100.

[0111] like Figure 4 As shown, in some embodiments, the main control circuit 110 includes: an analog front-end circuit 120 , an analog-to-digital conversion circuit 130 , a main control chip 140 , a digital-to-analog conversion circuit 150 and a valve drive circuit 160 .

[0112] The input end of the analog-to-digital conversion circuit 130 is electrically connected to the output end of the analog front-end circuit 120, and the output end of the analog-to-digital conversion circuit 130 is electrically connected to the input end of the main control chip 140; the input end of the digital-to-analog conversion circuit 150 is electrically connected to the output end of the main control chip 140, and the output end of the digital-to-analog conversion circuit 150 is electrically connected to the input end of the valve drive circuit 160.

[0113] The input end of the analog front-end circuit 120 is electrically connected to the first end of the main control circuit 110, and the output end of the valve drive circuit 160 is electrically connected to the second end of the main control circuit 110; the analog front-end circuit 120 is configured to further process the output signal of the sensor 100 circuit to obtain a first analog signal, and transmit the first analog signal to the analog-to-digital conversion circuit 130.

[0114] The valve driving circuit 160 is configured to control the opening of the valve and adjust the fluid flow.

[0115] Based on the above scheme, some embodiments of the present application provide a flow controller 200, which measures the flow size of the fluid pipeline in real time through the sensor 100 circuit, and feeds back the flow value to the main control circuit 110; the main control circuit 110 determines whether the fluid in the fluid pipeline is in a high-speed or low-speed state according to the detected flow value and the size of the preset range. When the flow exceeds the preset range, that is, it is in a high flow rate state at this time, the flow controller 200 works in a constant current mode; at this time, the path switching module 3 is connected with the constant current source control module 1, and the power is supplied by the constant current source control module 1, so that the current of the sensor 100 circuit is constant, and the power consumption will be reduced when the resistance is constant. When the flow does not exceed the preset range, that is, it is in a low flow rate state at this time, the flow controller 200 works in a constant temperature difference mode; at this time, the path switching module 3 is connected with the constant temperature difference control module 2, and the temperature difference between the upstream resistor Ru and the downstream resistor Rd and the ambient temperature can be controlled by the constant temperature difference control module 2 to be a constant value, which can further provide higher monitoring and control accuracy. That is to say, by adopting different working modes at different flow rates, high-precision flow measurement can be achieved in a wide flow range.

[0116] like Figure 5 As shown, Figure 5 The main control chip is the core control unit of the system, which connects various functional modules, including flow sensor, pressure sensor, other sensors, analog-to-digital conversion circuit, memory, user input unit, communication unit, digital-to-analog conversion circuit, valve drive circuit, power module and output unit.

[0117] The main control chip receives signals from the sensor, collects and processes them through the analog-to-digital conversion circuit, and adjusts the valve movement through the digital-to-analog conversion circuit and the valve drive circuit based on the processing results and the built-in control algorithm, so that the flow value is equal to the set target value, thereby realizing flow control.

[0118] In some embodiments, the output unit includes a display panel, indicator lights, analog outputs, etc., for displaying and outputting system status and measurement results.

[0119] The system detects the fluid flow rate in real time through the flow sensor. When the fluid flow rate exceeds the preset range, the main control circuit switches the power supply module and connection mode of the upstream resistor Ru and the downstream resistor Rd through the control path switching module 31-33, and selects to enter the constant current mode. The system outputs the control signal by selecting the matching control algorithm according to the sensor signals Vh and Vout in the constant current mode. Conversely, when the fluid flow rate is lower than the preset range and enters the constant temperature difference mode, the system selects the matching control algorithm according to the sensor signals Vu, Vd and Vout in the constant current mode and outputs the control signal.

[0120] If the system needs to detect stable flow signals for a long time without rapid adjustment and response, the user can also send instructions through the host computer to make the flow controller work in constant current mode to reduce system power consumption. And when in constant current mode, the system monitors that the flow rate decreases faster than the protection threshold, or the flow value is lower than a certain threshold, which may cause the sensor temperature to overheat, and the sensor should be switched to constant temperature difference mode in response.

[0121] The system is used in many fields: Semiconductor manufacturing: In the semiconductor manufacturing process, accurate control of gas flow is crucial to ensure process consistency and quality. The flow sensor of this application can be used to monitor and control the flow in the gas delivery system, ensuring high accuracy and low power consumption over different flow ranges.

[0122] Biopharmaceuticals: In the biopharmaceutical process, the precise control of liquid and gas flow has an important impact on the production process and product quality. The flow sensor of this application can be used in pharmaceutical equipment to monitor and adjust the flow of drug solution and culture medium in real time to ensure the stability and reliability of the process.

[0123] Environmental monitoring: In the field of environmental monitoring, gas flow sensors are used to monitor air quality, greenhouse gas emissions, etc. The flow sensor of this application can be installed in environmental monitoring equipment to monitor the concentration of pollutants in the air in real time and provide high-precision data to support environmental protection and governance.

[0124] Industrial Automation: In industrial automation systems, precise control of gas and liquid flow has a direct impact on the efficiency of the production line and product quality. The flow sensor of this application can be integrated into the automation control system to monitor and adjust the flow in real time to ensure the efficient operation of the production process.

[0125] Heating Ventilation and Air Conditioning (HVAC) system: HVAC system requires precise control of the flow of air and refrigerant to achieve energy saving and comfortable environment. The flow sensor of this application can be used to monitor and control the air flow and refrigerant flow, optimize system performance and reduce energy consumption.

[0126] Automotive industry: In automotive engines and emission control systems, gas flow sensors are used to monitor the flow of fuel and exhaust gases. The flow sensor of this application can be used in the intake and exhaust systems of automotive engines to provide real-time flow data, optimize engine performance and reduce emissions.

[0127] Chemical industry: Chemical production processes require precise control of gas and liquid flow rates to ensure the stability of reaction conditions and product quality. The flow sensor of this application can be used in chemical equipment to monitor and adjust flow rates in real time, thereby improving production efficiency and safety.

[0128] Laboratory research: In scientific research experiments, precise control of gas and liquid flow is crucial to the accuracy and repeatability of experimental results. The flow sensor of this application can be used in laboratory equipment to provide high-precision flow measurement and control to support various scientific research.

[0129] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0130] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0131] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A sensor, characterized in that: The sensor is connected to the fluid pipeline and is used to detect the flow value of the fluid in the fluid pipeline in real time; the sensor includes: Upstream resistance; a downstream resistor, the downstream resistor being arranged downstream of the upstream resistor; a constant current source control module, wherein the constant current source control module is configured to provide a stable current source in a constant current mode; a constant temperature difference control module, the constant temperature difference control module being configured to control the temperatures of the upstream resistor and the downstream resistor of the fluid pipeline in a constant temperature difference mode; A plurality of path switching modules, at least one of which has one end electrically connected to the first end of the upstream resistor of the fluid pipeline, and the other end electrically connected to the output end of the constant current source control module; at least one of which has one end electrically connected to the first end of the downstream resistor of the fluid pipeline, and the other end electrically connected to the output end of the constant temperature difference control module; at least one of which has one end electrically connected to the second end of the upstream resistor, and the other end electrically connected to the first end of the downstream resistor.

2. The sensor according to claim 1, characterized in that The multiple path switching modules include: a first path switching module, wherein a first end of the first path switching module is electrically connected to a first end of an upstream resistor of the fluid pipeline, a second end of the first path switching module is electrically connected to an output end of the constant current source control module; and a third end of the first path switching module is electrically connected to an output end of the constant temperature difference control module; a second path switching module, wherein a first end of the second path switching module is electrically connected to a second end of an upstream resistor of the fluid pipeline, and is also electrically connected to an input end of the constant current source control module; a second end of the second path switching module is electrically connected to a first end of a downstream resistor; and a third end of the second path switching module is electrically connected to a ground end; a third passage switching module, wherein a first end of the third passage switching module is electrically connected to a first end of a downstream resistor of the fluid pipeline, and a second end of the third passage switching module is electrically connected to an output end of the constant temperature difference control module; The first path switching module is configured to select a power supply mode for an upstream resistor of the fluid pipeline; The second path switching module is configured to select a connection mode of an upstream resistor and a downstream resistor of the fluid pipeline; The second path switching module is configured to select a power supply mode for a downstream resistor of the fluid pipeline.

3. The sensor according to claim 2, characterized in that The constant temperature difference control module comprises: a first bridge circuit, wherein a first end of the first bridge circuit is electrically connected to a third end of the first path switching module; and a second end of the first bridge circuit is electrically connected to the ground end; a second bridge circuit, wherein a first end of the second bridge circuit is electrically connected to a second end of the third path switching module; and a second end of the second bridge circuit is electrically connected to the ground end; a first operation circuit, wherein a first end of the first operation circuit is electrically connected to a third end of the first bridge circuit; and a second end of the first operation circuit is electrically connected to a third end of the second bridge circuit; a first signal adjustment circuit, wherein a first end of the first signal adjustment circuit is electrically connected to a third end of the first operation circuit; and a second end of the first signal adjustment circuit is electrically connected to a main control circuit; The first bridge circuit is configured to output a voltage signal of the upstream resistor and transmit the voltage signal to the first operation circuit; The second bridge circuit is configured to output a voltage signal of the downstream resistor and transmit the voltage signal to the first operation circuit; The first operation circuit is configured to calculate a difference between a voltage signal of the upstream resistor and a voltage signal of the downstream resistor.

4. The sensor according to claim 3, characterized in that The first bridge circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first transistor, and a first operational amplifier; The control end of the first transistor is electrically connected to the output end of the first operational amplifier, the first end of the first transistor is electrically connected to the first end of the fourth resistor, the second end of the first transistor is electrically connected to the second end of the fourth resistor, and is also electrically connected to the first end of the first resistor, the first end of the third resistor, and the third end of the first bridge circuit; The first input terminal of the first operational amplifier is electrically connected to the second terminal of the first resistor, and is also electrically connected to the first terminal of the second resistor, and the second terminal of the second resistor is electrically connected to the second terminal of the first bridge circuit; The second input terminal of the first operational amplifier is electrically connected to the second terminal of the third resistor, and is also electrically connected to the first terminal of the first bridge circuit.

5. The sensor according to claim 3, characterized in that The second bridge circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second transistor, and a second operational amplifier; The control end of the second transistor is electrically connected to the output end of the second operational amplifier, the first end of the second transistor is electrically connected to the first end of the eighth resistor, the second end of the second transistor is electrically connected to the second end of the eighth resistor, and is also electrically connected to the first end of the fifth resistor, the first end of the seventh resistor, and the third end of the second bridge circuit; The first input terminal of the second operational amplifier is electrically connected to the second terminal of the fifth resistor, and is also electrically connected to the first terminal of the sixth resistor, and the second terminal of the sixth resistor is electrically connected to the second terminal of the second bridge circuit; The second input terminal of the second operational amplifier is electrically connected to the second end of the seventh resistor, and is also electrically connected to the first end of the second bridge circuit.

6. The sensor according to claim 3, characterized in that The first operation circuit comprises: an instrumentation amplifier, wherein a first input terminal of the instrumentation amplifier is electrically connected to a first terminal of the first operational circuit, a second input terminal of the instrumentation amplifier is electrically connected to a second terminal of the first operational circuit; and an output terminal of the instrumentation amplifier is electrically connected to an output terminal of the first operational circuit; A ninth resistor, wherein a first end of the ninth resistor is electrically connected to the third input end of the instrument amplifier, and a second end of the ninth resistor is electrically connected to the fourth input end of the instrument amplifier.

7. The sensor according to claim 2, characterized in that The constant current source control module comprises: Constant current source, An adjustable resistor, wherein a first end of the adjustable resistor is electrically connected to an output end of the constant current source and is also electrically connected to a second end of the first path switching module, and a second end of the adjustable resistor is electrically connected to a main control circuit; a third bridge circuit, wherein a first end of the third bridge circuit is electrically connected to the first end of the adjustable resistor, and a second end of the third bridge circuit is electrically connected to the ground end; a second operation circuit, wherein a first end of the second operation circuit is electrically connected to a third end of the third bridge circuit, and a second end of the second operation circuit is electrically connected to a first end of the second path switching module; A second signal adjustment circuit, wherein a first end of the second signal adjustment circuit is electrically connected to a third end of the second operation circuit, and a second end of the second signal adjustment circuit is electrically connected to the main control circuit.

8. The sensor according to claim 7, characterized in that The third bridge circuit comprises: a tenth resistor and an eleventh resistor; The first end of the tenth resistor is electrically connected to the first end of the third bridge circuit, the second end of the tenth resistor is electrically connected to the first end of the eleventh resistor, and is also electrically connected to the third end of the third bridge circuit; The second end of the eleventh resistor is electrically connected to the second end of the third bridge circuit.

9. A flow controller, characterized in that: include: The sensor according to any one of claims 1 to 8; A main control circuit, the main control circuit is electrically connected to the output end of the sensor; multiple control ends of the main control circuit are electrically connected to the control ends of the multiple path switching modules; A valve, wherein the control end of the valve is electrically connected to the second end of the main control circuit; the valve is arranged at the outlet of the fluid pipeline, and the valve is configured to control the on-off of the fluid pipeline; The main control circuit is configured to switch the operation of the constant current source control module or the constant temperature difference control module according to the flow value detected by the sensor.

10. The flow controller according to claim 9, characterized in that: The main control circuit includes: an analog front-end circuit, an analog-to-digital conversion circuit, a main control chip, a digital-to-analog conversion circuit and a valve drive circuit; The input end of the analog-to-digital conversion circuit is electrically connected to the output end of the analog front-end circuit, and the output end of the analog-to-digital conversion circuit is electrically connected to the input end of the main control chip; The input end of the digital-to-analog conversion circuit is electrically connected to the output end of the main control chip, and the output end of the digital-to-analog conversion circuit is electrically connected to the input end of the valve drive circuit; The input end of the analog front-end circuit is electrically connected to the first end of the main control circuit, and the output end of the valve drive circuit is electrically connected to the second end of the main control circuit; The analog front-end circuit is configured to further process the output signal of the sensor to obtain a first analog signal, and transmit the first analog signal to the analog-to-digital conversion circuit; The valve driving circuit is configured to control the opening of the valve to adjust the fluid flow.

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