High-precision pneumatic switch sensor circuit based on MEMS thermal flow chip

Abstract

The utility model discloses a high-precision pneumatic switch sensor circuit based on an MEMS thermal flow chip, which relates to the technical field of thermal pneumatic switch sensing and comprises a power supply unit, a signal sensing unit and a data processing unit. The signal induction unit comprises an MEMS thermal flow chip, and the MEMS thermal flow chip is used for detecting gas flow and generating a differential voltage signal; the data processing unit converts the differential voltage signal generated by the signal induction unit into a digital quantity after A / D conversion and operation processing, a target flow value is obtained, and analog voltage is output through a DAC; the power supply unit supplies power to the signal induction unit and the data processing unit. The pneumatic switch sensor corresponding to the circuit has the advantages of small size, low power consumption, low cost, high reliability, long service life and the like by using an analog front end of the MEMS technology, and the MCU performs data processing and is convenient to access an application system of a client.

Description

Technical Field

[0001] This utility model relates to the field of pneumatic switch sensing technology, and in particular to a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip. Background Technology

[0002] Currently, gas flow measurement on the market mainly uses the principle of turbine or rotor plus Hall switch, which has shortcomings such as risk of jamming and poor sensitivity at low flow rates. It is necessary to solve these shortcomings while requiring low cost, long life and simple structure. Utility Model Content

[0003] This utility model aims to solve at least one of the technical problems existing in the prior art. To this end, this utility model proposes a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip. The pneumatic switch sensor composed of the electronic module in this utility model uses a MEMS technology analog front end, which has the characteristics of small size, low power consumption, low cost, high reliability, and long life. The MCU performs data processing, which is convenient for integration into the customer's application system.

[0004] According to an embodiment of the present invention, a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip is proposed, comprising: a power supply unit, a signal sensing unit, and a data processing unit.

[0005] The signal sensing unit includes a MEMS thermal flow chip, which detects the gas flow rate and generates a differential voltage signal.

[0006] The data processing unit converts the differential voltage signal generated by the signal sensing unit into a digital value through A / D conversion and arithmetic processing to obtain the target flow rate value, and outputs an analog voltage through a DAC.

[0007] The power supply unit provides power to the signal sensing unit and the data processing unit.

[0008] Furthermore, the power supply unit includes a power management chip and peripheral circuitry, with the following circuit connections: external DC power is input through socket J1; pin 1 (VI N) of socket J1 is connected to one end of the second bidirectional Zener diode; pin 2 (GND) of socket J1 is connected in parallel to ground with one end of the first bidirectional Zener diode, the other end of the second bidirectional Zener diode, pin 4 (GND) of socket J1, and pin 9 (NCS / SAO) of the data processing unit microprocessor chip; pin 3 (VOUT) of socket J1 is connected in parallel with the other end of the first bidirectional Zener diode and pin 14 (AODO) of the data processing unit microprocessor chip; pin 1 (VIN) of socket J1 is connected to the positive terminal of the third Zener diode, and the negative terminal of the third Zener diode... The first capacitor is connected in parallel with one end of the first capacitor, one end of the second capacitor, the IN pin of the power management chip, and the EN pin of the power management chip; the other ends of the first capacitor and the second capacitor are connected in parallel with the second pin of the power management chip to ground; the NC / FB pin of the power management chip is connected to one end of the first resistor and one end of the second resistor, and the other end of the second resistor is grounded; the other end of the first resistor is connected to one end of the third capacitor, one end of the fourth capacitor, and the OUT pin of the power management chip to provide power output; the other ends of the third capacitor and the other ends of the fourth capacitor are connected in parallel to ground.

[0009] Furthermore, the signal sensing unit includes a MEMS thermal conductivity flow chip, which includes a heater and a thermocouple. The power supply unit output VHT terminal is connected to one end of the 5th resistor, and the other end of the 5th resistor is connected to the 3rd pin HTR1 terminal of the MEMS thermal conductivity flow chip. The 6th pin HTR2 terminal of the MEMS thermal conductivity flow chip is grounded. The 1st pin UP+ terminal of the MEMS thermal conductivity flow chip thermocouple is connected to the 4th pin SIP terminal of the data processing unit microprocessor chip. The 2nd pin UP- terminal of the MEMS thermal conductivity flow chip thermocouple is connected in parallel with the 4th pin DWN- terminal, one end of the 7th capacitor, one end of the 3rd resistor, and one end of the 4th resistor. The 5th pin of the MEMS thermal conductivity flow chip thermocouple is connected in parallel with the 6th pin SIN terminal, one end of the 5th capacitor, and one end of the 9th capacitor of the data processing unit microprocessor chip.

[0010] Further, the data processing unit includes a microprocessor chip. The first pin (VDD) of the microprocessor chip is connected in parallel with the power supply unit output (VHT) and one end of the sixth capacitor. The other end of the sixth capacitor is connected in parallel to ground with the second pin (VSS), the seventh pin (IC), and the fifth pin (EPAD) of the microprocessor chip. The third pin (SVSS) of the microprocessor chip is connected in parallel with one end of the eighth capacitor, one end of the ninth capacitor, and one end of the fourth resistor. The fourth pin (SIP) of the microprocessor chip is connected in parallel with the first pin (UP+) of the MEMS thermal conductivity chip thermocouple, the other end of the eighth capacitor, and one end of the fifth capacitor. The fifth pin (SVDD) of the microprocessor chip is connected to one end of the third resistor. The sixth pin (SIN) of the microprocessor chip is connected in parallel with the other end of the ninth capacitor, the other end of the fifth capacitor, and the fifth pin (DWN+) of the MEMS thermal conductivity chip thermocouple. The fourth pin (AODO) of the microprocessor chip is connected to the third pin (VOUT) of the first socket. The eleventh pin (MI) of the microprocessor chip... The SO / SDA terminal is connected to the SDA terminal of pin 3 of socket 2; the SCK / SCL terminal of pin 10 of the microprocessor chip is connected to the SCL terminal of pin 2 of socket 2; the 9th pin of the microprocessor chip is connected to ground in parallel with the GND terminal of pin 4 of socket 2 and the GND terminal of pin 2 of socket 1; the VDD terminal of pin 1 of socket 2 is connected to the VHT terminal of the power supply unit output.

[0011] This utility model, based on the thermal principle, is a pneumatic switch sensor that overcomes the shortcomings of existing technologies that use turbines or rotors with Hall switches to measure gas flow, such as the risk of jamming and poor sensitivity at low flow rates. At the same time, it has the advantages of low cost, long life, and simple structure. Attached Figure Description

[0012] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0013] Figure 1 This is a schematic diagram of the power input principle of a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip according to an embodiment of the present invention.

[0014] Figure 2 This is a schematic diagram of the power supply unit of a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip according to an embodiment of the present invention.

[0015] Figure 3 This is a schematic diagram of the signal sensing unit of a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip according to an embodiment of the present invention.

[0016] Figure 4This is a schematic diagram of a high-precision pneumatic switch sensor circuit data processing unit based on a MEMS thermal flow chip according to an embodiment of the present invention.

[0017] Figure 5 This is a schematic diagram of the circuit principle of a high-precision pneumatic switch sensor based on a MEMS thermal flow chip according to an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0019] Reference Figures 1 to 5 This utility model discloses a high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip. The electronic module structure of this utility model can be divided into three parts: a power supply unit, a signal sensing unit, and a data processing unit.

[0020] The connection between the components is as follows: the power supply unit supplies power to the other components; the signal sensing unit detects the gas flow rate through a MEMS thermal flow meter and outputs the gas flow rate information as a voltage signal; the data processing unit analyzes and processes the voltage signal detected by the MEMS thermal flow meter through a built-in multi-channel 16-bit Delta Sigma A / D converter and outputs an analog voltage.

[0021] Please refer to Figures 1 to 5 This embodiment further illustrates the working principle of each part. First, the power supply unit is introduced. Based on the MEMS thermal flow chip high-precision pneumatic switch sensor, the external power required by the sensor is input through socket J1, providing a 24V DC input power to the entire sensor circuit. The power supply unit circuit provides a 5.2V power supply to the MEMS thermal flow chip through an LDO. For details, please refer to... Figure 1 and Figure 2 The power supply unit circuit is briefly described below:

[0022] The power supply unit includes a power management chip and peripheral circuitry. The circuit connections are as follows: After external DC power is input through socket J1, pin 1 (VIN) of socket J1 is connected to one end of the second bidirectional Zener diode; pin 2 (GND) of socket J1 is connected in parallel to one end of the first bidirectional Zener diode, the other end of the second bidirectional Zener diode, pin 4 (GND) of socket J1, and pin 9 (NCS / SAO) of the data processing unit microprocessor chip; pin 3 (VOUT) of socket J1 is connected in parallel to the other end of the first bidirectional Zener diode and pin 14 (AODO) of the data processing unit microprocessor chip; pin 1 (VI) of socket J1... The N terminal is connected to the positive terminal of the third Zener diode. The negative terminal of the third Zener diode is connected in parallel to one end of the first capacitor, one end of the second capacitor, the IN terminal of the first pin of the power management chip, and the EN terminal of the third pin of the power management chip. The other ends of the first and second capacitors are connected in parallel to the second pin of the power management chip and grounded. The NC / FB terminal of the fourth pin of the power management chip is connected to one end of the first and second resistors, and the other end of the second resistor is grounded. The other end of the first resistor is connected to one end of the third and fourth capacitors and the OUT terminal of the fifth pin of the power management chip to provide power output. The other ends of the third and fourth capacitors are connected in parallel to grounded. In this embodiment, the external power input can be selected from 6V to 24V DC power supply, and the DC voltage output by the VHT terminal of the power management chip is 5.2V.

[0023] In this embodiment, the power unit management chip can be selected as the following model:

[0024] Reference Figure 3 and Figure 5 The high-precision pneumatic switch sensor signal sensing unit based on the MEMS thermal flow chip in this embodiment will be further explained as follows:

[0025] An advanced MEMS thermal conductivity chip is used as the sensing device. After a stable voltage is provided to the heater of the thermal conductivity chip, the heater heats the insulating base, and the thermocouple generates a millivolt output. When the gas passing through the sensor chip is not flowing, the differential output voltage of the thermocouple is zero. If the gas flows across the surface of the sensor chip, the upstream thermocouple is cooled by the medium. The flowing gas, after passing through the heater, transfers heat to the downstream thermocouple. The differential voltage signal output by the thermocouple (downstream minus upstream) changes with the gas flow rate. In this embodiment, the upstream thermocouple outputs are UP+ and UP-, and the downstream thermocouple outputs are DWN+ and DWN-.

[0026] Specifically, the circuit connection relationship is briefly explained as follows:

[0027] The MEMS thermal conductivity chip includes a heater and a thermocouple. The power supply unit output VHT terminal is connected to one end of the 5th resistor, and the other end of the 5th resistor is connected to the 3rd pin HTR1 terminal of the MEMS thermal conductivity chip. The 6th pin HTR2 terminal of the MEMS thermal conductivity chip is grounded. The 1st pin UP+ terminal of the MEMS thermal conductivity chip thermocouple is connected to the 4th pin SIP terminal of the data processing unit microprocessor chip. The 2nd pin UP- terminal of the MEMS thermal conductivity chip thermocouple is connected in parallel with the 4th pin DWN- terminal, one end of the 7th capacitor, one end of the 3rd resistor, and one end of the 4th resistor. The 5th pin of the MEMS thermal conductivity chip thermocouple is connected in parallel with the 6th pin SIN terminal, one end of the 5th capacitor, and one end of the 9th capacitor of the data processing unit microprocessor chip.

[0028] In this embodiment, the MEMS thermal flow chip for the signal sensing unit can be selected as model PTFD21.

[0029] Please refer to Figure 4 and Figure 5 The data processing unit of the high-precision pneumatic switch sensor circuit based on the MEMS thermal flow chip in this embodiment will be further explained as follows:

[0030] The data processing unit is mainly a microprocessor chip, or MCU for short, with a built-in multi-channel 16-bit ADC. This MCU detects MEMS voltage signals, then performs internal A / D conversion and processing to convert these signals into 16-bit digital quantities to obtain the target flow rate value, and finally outputs analog voltage through a DAC.

[0031] The microprocessor chip's pin 1 (VDD) is connected in parallel with the power supply unit's output (VHT) and one end of capacitor 6; the other end of capacitor 6 is connected in parallel with the microprocessor chip's pin 2 (VSS), pin 7 (IC), and pin 15 (EPAD) to ground; the microprocessor chip's pin 3 (SVSS) is connected in parallel with one end of capacitor 8, one end of capacitor 9, and one end of resistor 4; the microprocessor chip's pin 4 (SIP) is connected in parallel with the MEMS thermal conductivity chip's thermocouple pin 1 (UP+), the other end of capacitor 8, and one end of capacitor 5; the microprocessor chip's pin 5 (SVDD) is connected to one end of resistor 3; the microprocessor chip's pin 6 (SIN) is connected in parallel with the other end of capacitor 9, the other end of capacitor 5, and the MEMS thermal conductivity chip's thermocouple pin 5 (DWN+); the microprocessor chip's pin 14 (AODO) is connected to the first socket's pin 3 (VOUT); the microprocessor chip's pin 11 (MI)... The SO / SDA terminal is connected to the SDA terminal of pin 3 of socket 2; the SCK / SCL terminal of pin 10 of the microprocessor chip is connected to the SCL terminal of pin 2 of socket 2; the 9th pin of the microprocessor is connected to ground in parallel with the GND terminal of pin 4 of socket 2 and the GND terminal of pin 2 of socket 1; the VDD terminal of pin 1 of socket 2 is connected to the VHT terminal of the power supply unit output.

[0032] In this embodiment, the data processed by the data processing unit is output to the outside through the J2 socket.

[0033] In this embodiment, the microcontroller (MCU) chip for the data processing unit can be selected as model E703.11.

[0034] Based on the above scheme, a high-precision pneumatic switch sensor based on a MEMS thermal flow chip is designed. The pneumatic switch sensor uses MEMS technology for the analog front end, which features small size, low power consumption, low cost, high reliability, and long life. The MCU performs data processing, making it easy to integrate into the customer's application system.

[0035] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

[0036] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0037] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A high-precision pneumatic switch sensor circuit based on a MEMS thermal flow chip, characterized in that, include: Power supply unit, signal sensing unit, data processing unit; The signal sensing unit includes a MEMS thermal flow chip, which detects gas flow and generates a differential voltage signal. The data processing unit converts the differential voltage signal generated by the signal sensing unit into a digital value through A / D conversion and arithmetic processing to obtain the target flow rate value, and outputs an analog voltage through a DAC. The power supply unit is the signal sensing unit, which provides power to the data processing unit.

2. The high-precision MEMS thermal flow chip-based pneumatic switch sensor circuit according to claim 1, characterized in that, The power supply unit includes a power management chip and peripheral circuitry. The circuit connections are as follows: external DC power is input through socket J1; pin 1 (VIN) of socket J1 is connected to one end of the second bidirectional Zener diode; pin 2 (GND) of socket J1 is connected in parallel to one end of the first bidirectional Zener diode, the other end of the second bidirectional Zener diode, pin 4 (GND) of socket J1, and pin 9 (NCS / SAO) of the data processing unit microprocessor chip; pin 3 (VOUT) of socket J1 is connected in parallel to the other end of the first bidirectional Zener diode and pin 14 (AODO) of the data processing unit microprocessor chip; pin 1 of socket J1... The VIN pin is connected to the positive terminal of the third Zener diode. The negative terminal of the third Zener diode is connected in parallel to one end of the first capacitor, one end of the second capacitor, the IN pin of the power management chip, and the EN pin of the power management chip. The other ends of the first and second capacitors are connected in parallel to the second pin of the power management chip and grounded. The NC / FB pin of the power management chip is connected to one end of the first and second resistors, and the other end of the second resistor is grounded. The other end of the first resistor is connected to one end of the third and fourth capacitors and the OUT pin of the power management chip to provide power output. The other ends of the third and fourth capacitors are connected in parallel to grounded.

3. The high-precision MEMS thermal flow chip-based pneumatic switch sensor circuit according to claim 1, characterized in that, The signal sensing unit includes a MEMS thermal conductivity chip, which includes a heater and a thermocouple. The power supply unit outputs a VHT terminal connected to one end of a 5th resistor, and the other end of the 5th resistor is connected to the 3rd pin (HTR1) of the MEMS thermal conductivity chip. The 6th pin (HTR2) of the MEMS thermal conductivity chip is grounded. The 1st pin (UP+) of the MEMS thermal conductivity chip thermocouple is connected to the 4th pin (SIP) of the data processing unit microprocessor chip. The 2nd pin (UP-) of the MEMS thermal conductivity chip thermocouple is connected in parallel with the 4th pin (DWN-), one end of the 7th capacitor, one end of the 3rd resistor, and one end of the 4th resistor. The 5th pin of the MEMS thermal conductivity chip thermocouple is connected in parallel with the 6th pin (SIN), one end of the 5th capacitor, and one end of the 9th capacitor of the data processing unit microprocessor chip.

4. The high-precision MEMS thermal flow chip-based pneumatic switch sensor circuit according to claim 1, characterized in that, The data processing unit includes a microprocessor chip, the first pin VDD end of the microprocessor chip is connected with the power unit output VHT end and the first end of the sixth capacitor in parallel; the other end of the sixth capacitor is connected with the second pin VSS end of the microprocessor chip, the seventh pin IC end of the microprocessor chip, the fifteenth pin EPAD end of the microprocessor chip and ground in parallel; the third pin SVSS end of the microprocessor chip is connected with the first end of the eighth capacitor, the first end of the ninth capacitor and the first end of the fourth resistor in parallel; the fourth pin SIP end of the microprocessor chip is connected with the first pin UP+ of the signal sensing unit MEMS thermal conductivity flow chip thermocouple, the other end of the eighth capacitor, the first end of the fifth capacitor in parallel; the fifth pin SVDD end of the microprocessor chip is connected with the first end of the third resistor; the sixth pin SIN end of the microprocessor chip is connected with the other end of the ninth capacitor, the other end of the fifth capacitor and the fifth pin DWN+ end of the signal sensing unit MEMS thermal conductivity flow chip thermocouple in parallel; the fourteenth pin AODO end of the microprocessor chip is connected with the third pin VOUT end of the first socket; the eleventh pin MISO / SDA end of the microprocessor chip is connected with the third pin SDA end of the second socket; the tenth pin SCK / SCL end of the microprocessor chip is connected with the second pin SCL end of the second socket; the ninth pin of the microprocessor chip is connected with the fourth pin GND end of the second socket, the second pin GND end of the first socket and ground in parallel; the first pin VDD end of the second socket is connected with the power unit output VHT end.

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