A thermal flow sensor acceleration field compensation method

Abstract

The present application relates to the technical field of sensor, in particular to a kind of thermal flow sensor acceleration field compensation method.The present application embodiment provides a kind of thermal flow sensor acceleration field compensation method, comprising: in the U-shaped flow channel of one end gas one end gas setting position two sensor chips;Two sensor chips are respectively arranged in the two parallel channel parts of the U-shaped flow channel, and two sensor chips are symmetrically distributed;First output signal and second output signal are respectively collected using two sensor chips;According to the first output signal and the second output signal, data compensation is carried out, and only forced convection signal caused by gas flow is obtained.The present application embodiment provides a kind of thermal flow sensor acceleration field compensation method, can realize the mathematical separation and offset of natural convection component, to effectively inhibit acceleration field interference.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a method for acceleration field compensation of a thermal flow sensor. Background Technology

[0002] This invention relates to the application of microelectromechanical system (MEMS) sensors in gas flow measurement with high precision and anti-interference capabilities. In particular, it proposes an innovative compensation scheme and circuit design to address the working problem of thermal gas flow sensors in complex acceleration field environments.

[0003] Traditional thermal flow sensors typically rely on the coordinated operation of a heating resistor and a temperature-sensing resistor within the sensor chip: the heating resistor heats the gas, and as the gas flows, heat transfer creates a temperature difference between the upstream and downstream sides. This temperature difference is detected by symmetrically distributed temperature-sensing resistors and converted into an electrical signal, thus characterizing the gas flow rate. However, in practical applications such as aerospace propulsion systems, vehicle power monitoring, industrial process control, and mobile platform equipment, acceleration fields significantly induce natural convection effects after the gas is heated. This results in the sensor output signal being a mixture of forced convection and natural convection, severely reducing the accuracy and reliability of the measurement. Summary of the Invention

[0004] This invention provides a method for acceleration field compensation of a thermal flow sensor, which can achieve mathematical separation and cancellation of natural convection components, thereby effectively suppressing acceleration field interference.

[0005] This invention provides a method for acceleration field compensation of a thermal flow sensor, comprising: Two sensor chips are positioned in a U-shaped flow channel with gas entering at one end and gas exiting at the other end; wherein the two sensor chips are respectively located in two parallel channel sections of the U-shaped flow channel, and the two sensor chips are symmetrically distributed; The first output signal and the second output signal are acquired using the two sensor chips respectively. Data compensation is performed based on the first output signal and the second output signal to obtain a forced convection signal that only contains gas flow.

[0006] In one possible design, the use of two sensor chips to acquire the first output signal and the second output signal respectively includes: A constant power heating resistor drive circuit is used to provide a stable drive current for the two sensor chips.

[0007] In one possible design, the constant power heating resistor drive circuit is a symmetrical dual-loop closed-loop control architecture. Each of the closed-loop control architectures consists of an operational amplifier, a power transistor, and an external resistor network, which together drive the heating resistor in the sensor chip. The non-inverting input of the operational amplifier is connected to the reference power supply. The current of the heating resistor flows through the precision sampling resistor of the peripheral resistor network and is converted into a voltage signal that is fed back to the inverting input of the operational amplifier, forming a current negative feedback. The operational amplifier compares the difference between the reference voltage and the feedback voltage for setting the heating power and outputs a control signal to the base of the power transistor. By adjusting the conduction level of the power transistor, the current of the heating power is dynamically adjusted to ensure constant power.

[0008] In one possible design, the step of performing data compensation based on the first output signal and the second output signal to obtain a forced convection signal containing only the forced convection signal caused by gas flow includes: The first and second output signals are differentially amplified and summed using a temperature-sensing resistor addition and subtraction circuit to obtain a forced convection signal that contains only the gas flow.

[0009] In one possible design, the temperature measurement addition / subtraction circuit includes a multi-stage operational amplifier, a resistor network, and a core computing unit; The first output signal and the second output signal are amplified by a multi-stage operational amplifier and then transmitted to the addition and subtraction circuits of the core arithmetic unit. The addition and subtraction circuits work in conjunction with the resistor network to perform calculations.

[0010] In one possible design, both sensors are MEMS sensor chips.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects: The core design employs a dual-sensor chip layout with a U-shaped flow channel. Symmetrical mounting ensures that the gas flow directions of the two chips are collinear but opposite. Under acceleration field interference, the output signals of the two chips exhibit complementary characteristics: one chip outputs "forced convection + natural convection," while the other outputs "forced convection - natural convection." By introducing an adjustable correlation coefficient, the mathematical separation and cancellation of the natural convection component can be achieved, effectively suppressing acceleration field interference. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 U-shaped flow channel design; Figure 2 Heating resistor drive circuit; Figure 3 Temperature sensing resistor addition and subtraction circuit; Figure 4 General structure of MEMS thermal flow meter; Figure 5 The effect of gravitational field on temperature distribution. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0016] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0017] Please refer to Figure 1 This invention provides a method for compensating the acceleration field of a thermal flow sensor, comprising: Two sensor chips are positioned in a U-shaped flow channel with gas entering at one end and gas exiting at the other end; the two sensor chips are respectively located in two parallel channel sections of the U-shaped flow channel, and the two sensor chips are symmetrically distributed. Two sensor chips are used to collect the first output signal and the second output signal, respectively. Data compensation is performed based on the first and second output signals to obtain a forced convection signal that contains only the gas flow.

[0018] The core design employs a dual-sensor chip layout with a U-shaped flow channel. Symmetrical mounting ensures that the gas flow directions of the two chips are collinear but opposite. Under acceleration field interference, the output signals of the two chips exhibit complementary characteristics: one chip outputs "forced convection + natural convection," while the other outputs "forced convection - natural convection." By introducing an adjustable correlation coefficient, the mathematical separation and cancellation of the natural convection component can be achieved, effectively suppressing acceleration field interference.

[0019] Specifically, two thermal flowmeter chips are used for flow measurement. Assuming the signals generated on the MEMS chips by forced convection due to gas flow and natural convection caused by acceleration are U1 and U2, respectively, the core objective of this scheme is to separate the U1 and U2 signals from the two MEMS thermal sensors. Its working principle lies in cleverly utilizing the different response characteristics of this symmetrical structure to forced convection and natural convection signals. When an external acceleration field is present, it induces natural convection of the gas, the direction of which is determined by the direction of acceleration. Therefore, for the two chips arranged symmetrically in space, the polarity of the natural convection interference signal is the same. Simultaneously, since the direction of forced convection is opposite at the two chips, the polarity of the forced convection signal is opposite.

[0020] The two sensors are located along the same collinear but opposite directions of gas flow. When an external acceleration field is applied, the output signals of the two sensors are the forced convection signal plus the natural convection signal and the forced convection signal minus the natural convection signal, respectively, as shown in the following equation: U A =U 1A +U 2A U B =U 1B -U 2B U A U B These represent the output signals of chips A and B, respectively. 1A U 2A U 1B U 2B Let U and B represent the forced convection and natural convection signal output components of chip A and chip B, respectively. Assume there exists a relationship coefficient k between sensors A and B such that U... 2A -k×U 2B =0: U0=U 1A +k×U 2B U0 contains only the forced convection signal caused by gas flow, which can compensate for the interference signal of natural convection caused by acceleration field.

[0021] In some embodiments of the present invention, two sensor chips are used to collect a first output signal and a second output signal, respectively, including: A constant power heating resistor drive circuit is used to provide a stable drive current for the two sensor chips.

[0022] In some embodiments of the present invention, the constant power heating resistor driving circuit is a symmetrical dual-loop closed-loop control architecture. Each closed-loop control architecture includes an operational amplifier, a power transistor and an external resistor network, which together drive the heating resistor in the sensor chip. The non-inverting input of the operational amplifier is connected to the reference power supply. The current of the heating resistor flows through the precision sampling resistor of the external resistor network and is converted into a voltage signal that is fed back to the inverting input of the operational amplifier, forming a current negative feedback. The operational amplifier compares the difference between the reference voltage and the feedback voltage for setting the heating power and outputs a control signal to the base of the power transistor. By adjusting the conduction level of the power transistor, the current of the heating power is dynamically adjusted to ensure constant power.

[0023] To ensure the stability and reliability of sensor operation and avoid additional measurement errors caused by fluctuations in heating power, this invention designs a constant power heating resistor drive circuit. This circuit provides a stable and precise drive current to the heating resistor in the MEMS chip, as shown in the specific circuit diagram. Figure 2 As shown, its core working principle is as follows: It employs a closed-loop control architecture, using a precision resistor to monitor the heating current in real time. This feedback signal is then compared and amplified with a stable reference voltage to control the output of the power devices. This design automatically compensates for changes in the heating resistor's resistance caused by power supply voltage fluctuations or ambient temperature changes, thereby maintaining a constant power on the heating resistor and providing a stable initial temperature field for flow sensing. This is the fundamental prerequisite for subsequent high-precision signal separation and compensation.

[0024] The specific implementation is as follows: The circuit adopts a symmetrical dual-loop closed-loop control architecture. Each loop consists of a precision operational amplifier (U1, U2), power transistors (Q1, Q2), and an external resistor network (R1-R4, Ra-Rf), which together drive the heating resistors (RH1, RH2) in the MEMS chip. During operation, the reference voltage source Vs is input to the non-inverting input of the operational amplifier to set the reference voltage corresponding to the target heating power. The current of the heating resistor RH1 (or RH2) flows through the precision sampling resistor R1 (or R2), converting it into a voltage signal and feeding it back to the inverting input of the operational amplifier, forming current negative feedback. The operational amplifier (U1 / U2) acts as an error comparator, continuously comparing the difference between the reference voltage and the feedback voltage, and outputs a control signal to the base of the power transistors (Q1 / Q2). By adjusting the conduction level of the transistors, the current flowing through the heating resistor is dynamically adjusted. This closed-loop control mechanism can compensate in real time for the effects of power supply voltage fluctuations or changes in the resistance of the heating resistor itself with temperature, thereby stabilizing the heating power at the set value. The entire design, through symmetrical dual-path independent control, ensures that the heating conditions of the two MEMS sensing chips are highly consistent, providing a crucial and stable thermal field foundation for subsequent accurate temperature difference detection and signal separation, and improving the measurement consistency and reliability of the sensor in complex environments.

[0025] In some embodiments of the present invention, data compensation is performed based on the first output signal and the second output signal to obtain a forced convection signal containing only the gas flow, including: The first and second output signals are differentially amplified and summed using a temperature-sensing resistor addition and subtraction circuit to obtain a forced convection signal that contains only the gas flow.

[0026] In some embodiments of the present invention, the temperature measurement addition / subtraction circuit includes a multi-stage operational amplifier, a resistor network, and a core arithmetic unit; The first and second output signals are amplified by a multi-stage operational amplifier and then transmitted to the adder and subtractor circuits of the core arithmetic unit. The adder and subtractor circuits, in conjunction with a resistor network, perform calculations.

[0027] The temperature measurement addition / subtraction circuit is the core of the entire acceleration field interference compensation scheme. Its core function is to process and analyze the raw signals output by two symmetrically mounted MEMS sensors in the front U-shaped flow channel in real time. This circuit system uses a highly integrated analog computing unit, primarily an addition / subtraction circuit based on a precision amplifier and resistor network, to perform specific calculations: it first receives two raw voltage signals containing forced convection and natural convection components with specific polarity relationships. Then, through precise differential amplification and summation, it intelligently separates the pure forced convection signal generated solely by gas flow, while effectively suppressing or canceling the common-mode interference signal of natural convection caused by the acceleration field. Furthermore, the circuit design incorporates an adjustable gain stage. By adjusting a potentiometer or using digital control, the amplification factor of one signal can be dynamically fine-tuned to precisely match any slight performance differences between the two sensors, thereby ensuring optimal interference cancellation. The entire circuit design not only possesses high reliability and real-time performance, meeting the rapid response requirements in complex dynamic environments, but its analog processing method also avoids the delay and power consumption problems caused by complex digital algorithms. Ultimately, it provides crucial hardware support and engineering implementation path for achieving high-precision and anti-interference measurement of thermal gas flow sensors in high-acceleration and high-vibration environments.

[0028] The specific implementation is as follows: (e.g.) Figure 3 As shown, the circuit is constructed using multi-stage operational amplifiers (U3-U6) and a precision resistor network (R1-R12). First, the temperature-sensing resistor signals from chip A and chip B are connected via a Wheatstone bridge to the first-stage instrumentation amplifier circuit composed of operational amplifiers U3 and U4, respectively. Its main function is to initially amplify the weak signals and suppress common-mode noise introduced during transmission. Subsequently, the two pre-amplified signals are sent to the core arithmetic unit, such as a subtractor circuit composed of operational amplifier U5 and an adder circuit composed of operational amplifier U6. In this stage, the resistance values ​​of resistors R7-R13 are precisely matched to set accurate arithmetic coefficients: the subtractor effectively cancels out the natural convection interference signal shared by the two chips by calculating the difference between the two signals (UA - UB), thereby extracting and amplifying the difference between the forced convection signals of opposite polarity; while the adder enhances the effective common-mode signal by calculating the sum of the two signals (UA + UB). Ultimately, this circuit, through this hardware-implemented combination of addition and subtraction, can complete the signal separation algorithm in real time without complex digital processing, and directly output a pure forced convection component. It is a key electronic implementation method for achieving acceleration field interference compensation.

[0029] Please refer to Figure 4 and Figure 5 In some embodiments of the present invention, both sensors are MEMS sensor chips.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for compensating the acceleration field of a thermal flow sensor, characterized in that, include: Two thermal flow sensor chips are positioned in a U-shaped flow channel with gas entering at one end and gas exiting at the other end; wherein the two thermal flow sensor chips are respectively located in two parallel channel sections of the U-shaped flow channel, and the two thermal flow sensor chips are symmetrically distributed. The first output signal and the second output signal are acquired using the two thermal flow sensor chips, respectively. Data compensation is performed based on the first output signal and the second output signal to obtain a forced convection signal that only contains gas flow.

2. The acceleration field compensation method according to claim 1, characterized in that, The method of using two thermal flow sensor chips to collect the first output signal and the second output signal respectively includes: A constant power heating resistor drive circuit is used to provide a stable drive current for the two thermal flow sensor chips.

3. The acceleration field compensation method according to claim 2, characterized in that, The constant power heating resistor drive circuit is a symmetrical dual-loop closed-loop control architecture. Each of the closed-loop control architectures consists of an operational amplifier, a power transistor, and an external resistor network, which together drive the heating resistor in the sensor chip. The non-inverting input of the operational amplifier is connected to the reference power supply. The current of the heating resistor flows through the precision sampling resistor of the peripheral resistor network and is converted into a voltage signal that is fed back to the inverting input of the operational amplifier, forming a current negative feedback. The operational amplifier compares the difference between the reference voltage and the feedback voltage for setting the heating power and outputs a control signal to the base of the power transistor. By adjusting the conduction level of the power transistor, the current of the heating power is dynamically adjusted to ensure constant power.

4. The acceleration field compensation method according to claim 1, characterized in that, The step of performing data compensation based on the first output signal and the second output signal to obtain a forced convection signal containing only the gas flow includes: The first and second output signals are differentially amplified and summed using a temperature-sensing resistor addition and subtraction circuit to obtain a forced convection signal that contains only the gas flow.

5. The acceleration field compensation method according to claim 4, characterized in that, The temperature measuring resistor addition and subtraction circuit includes a multi-stage operational amplifier, a resistor network, and a core computing unit; The first output signal and the second output signal are amplified by a multi-stage operational amplifier and then transmitted to the addition and subtraction circuits of the core arithmetic unit. The addition and subtraction circuits work in conjunction with the resistor network to perform calculations.

6. The acceleration field compensation method according to claim 1, characterized in that, Both of the sensors are MEMS sensor chips.

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