Small range high precision differential pressure transmitter

Abstract

The application discloses a small-range high-precision differential pressure transmitter and belongs to the technical field of pressure measurement and sensing. The circuit system of the application comprises a signal input module, a processing chip, a signal amplification module and a protection module. An external power supply is electrically connected with the processing chip to supply power to the signal input module. The signal input module electrically connects an external differential pressure sensor with the processing chip. The signal amplification module comprises an output triode Q2. The output pin of the processing chip is connected with the base of Q2 through a resistor R3 and is connected with the collector of Q2 through a capacitor C5. The collector of Q2 is electrically connected with the protection module after being stepped down through a resistor R4 and a resistor R5. The protection module is used to couple the high-frequency transient noise on the collector of Q2 to the output of a bidirectional TVS tube D3 after low-frequency decoupling and intermediate-frequency filtering of Q2. The application can realize small-range pressure measurement, constant-current power supply and millivolt signal output.

Description

Technical Field

[0001] This invention relates to the field of pressure measurement and sensing technology, and more specifically, to a small-range, high-precision differential pressure transmitter. Background Technology

[0002] While existing differential pressure transmitters on the market meet conventional pressure measurement needs to a certain extent, they still have the following significant technical shortcomings when applied to demanding applications requiring ultra-small measurement ranges and high precision: (1) The zero-point drift and temperature drift problems are serious, making it difficult to achieve stability under ultra-small range; (2) The installation location is sensitive, and static pressure can cause measurement failure; (3) On-site commissioning is inefficient and cannot adapt to complex working conditions; (4) Response speed and accuracy are mutually restrictive. Summary of the Invention

[0003] To address the aforementioned problems in existing technologies, the present invention aims to provide a small-range, high-precision differential pressure transmitter. It can compensate for zero-point and temperature drift through digital algorithms, and also allows for on-site commissioning, enabling calibration without a standard pressure source. Furthermore, structural optimization reduces the impact of installation stress.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows: A small-range, high-precision differential pressure transmitter includes: a signal input module, a processing chip, a signal amplification module, and a protection module. An external power supply is electrically connected to the processing chip to power the signal input module. The signal input module electrically connects an external differential pressure sensor to the processing chip. The output port of the processing chip is electrically connected to the signal amplification module. The signal amplification module is electrically connected to the protection module. The signal amplification module includes an output transistor Q2. The output pin of the processing chip is connected to the base of Q2 through a resistor R3, and simultaneously connected between the base and collector of Q2 through a capacitor C5. The collector of Q2 is electrically connected to the protection module after being stepped down by resistors R4 and R5. The protection module includes multiple capacitors connected to the signal amplification module to couple high-frequency transient noise on the collector of Q2 to a bidirectional TVS diode D3 for output after low-frequency decoupling and intermediate-frequency filtering of Q2.

[0005] The signal input module includes positive / negative current ports and positive / negative differential signal ports. The positive / negative current ports are connected to the IEXC1 and GND pins of the processing chip, respectively, and the positive / negative differential signal ports are connected to the VIP and VIN pins of the processing chip. The positive / negative differential signal ports are also grounded through capacitors C6 and C7 for filtering. The processing chip also integrates a TEMP pin for temperature detection, which is electrically connected to the positive current port. The signal amplification module also includes capacitor C4, resistor R2, and capacitor C3. The processing chip also includes an OWI pin, an FBN pin, and a Fil pin. One end of capacitor C4 is connected to the Fil pin for filtering, and the other end is grounded. One end of resistor R2 is connected to the OWI pin for current limiting, and the other end is connected to the protection module through capacitor C3.

[0006] Furthermore, the protection module includes capacitors C0, C16, and C14, a high-frequency filter bead B1, and a high-frequency filter bead B2. The two ends of capacitor C0 are connected to the emitter and collector of Q2, respectively. The two ends of capacitor C16 are connected to capacitor C3 and the collector of Q2, respectively. One end of high-frequency filter bead B1 is connected to the chassis ground through capacitor C14, and the other end is connected to the bidirectional TVS diode D3. One end of high-frequency filter bead B2 is connected to the chassis ground through capacitor C15, and the other end is connected to the bidirectional TVS diode D3.

[0007] Furthermore, a bidirectional TVS diode D4 is connected to the external power supply, and a varistor R0 is connected in series between D3 and D4.

[0008] Furthermore, the differential pressure sensor is model SSCL04DF.

[0009] Furthermore, the processing chip is model NSA2862.

[0010] Furthermore, a small-range, high-precision differential pressure transmitter also includes a housing, which is divided into upper and lower layers and connected by fixing screws. The top of the housing has an integrated port connector for electrically connecting to the processing chip, and the bottom of the housing has an air nozzle for connecting to an external air pipe.

[0011] Furthermore, the top surface of the housing is also integrated with a display screen, which is integrated with the small-range high-precision differential pressure transmitter via a microcontroller, the microcontroller model being HC32L136J8TA.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This device uses the SSCL04DF high-stability differential pressure sensor as the pressure sensing element. It achieves pressure measurement within a range of less than 1 kPa, is powered by constant current, outputs a millivolt signal, and converts the acquired signal into a standard current signal through an amplifier circuit.

[0013] This device can convert millivolt signals into standard current signals for output. After calibration, it achieves high precision. On-site pressure calibration and passive range shifting can be performed using a manual adjuster.

[0014] This device can be integrated with a microcontroller to achieve display circuit output, enabling automatic zeroing and calibration upon power-on, and displaying pressure and current values ​​on an LCD screen. The circuit also retains a communication interface, allowing for range shifting, calibration, and excitation in the field.

[0015] This equipment features a customized transmitter design and circuitry, enabling measurements of differential pressures less than 1 kPa. It achieves an accuracy of 0.5 class within the 25±5℃ range and a temperature drift of ±3%FS within the 0~50℃ range. Through circuit algorithms and physical ports, it enables on-site range migration and automatic calibration. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 This is a schematic diagram of the overall circuit structure of the present invention.

[0018] In the diagram: 1. Fixing screw; 2. Display screen; 3. Port connector; 4. Air nozzle; 5. Button; 6. Housing; 7. Signal input module; 8. Processing chip; 9. Signal amplification module; 10. Protection module. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments.

[0020] In this embodiment, for the overall structure, a small-range, high-precision differential pressure transmitter includes: a signal input module 7, a processing chip 8, a signal amplification module 9, and a protection module 10. An external power supply is electrically connected to the processing chip 8 to power the signal input module 7. The signal input module 7 electrically connects an external differential pressure sensor to the processing chip 8. The output port of the processing chip 8 is electrically connected to the signal amplification module 9, and the signal amplification module 9 is electrically connected to the protection module 10.

[0021] In actual selection, the differential pressure sensor is model SSCL04DF, and the processing chip 8 is model NSA2862. In the signal input module 7, the terminal interfaces include positive / negative current ports and positive / negative differential signal ports. The positive / negative current ports are connected to the IEXC1 pin and GND pin of the processing chip 8, respectively, and the positive / negative differential signal ports are connected to the VIP pin and VIN pin of the processing chip 8, respectively. The positive / negative differential signal ports are also grounded through capacitors C6 and C7 for filtering.

[0022] I+ and I- are the aforementioned positive / negative current ports, representing the positive and negative terminals of the sensor's excitation current. After being connected to the processing chip 8, they provide a constant current excitation source for the pressure sensor. The AVDD and DVDD pins are connected to an external power supply V+. O+ and O- are the aforementioned positive / negative differential signal ports, representing the positive and negative terminals of the sensor's differential signal output. These are subsequently connected to the processing chip 8 as input signals. Each of the O+ and O- lines has a 10nF capacitor (C6 and C7) connected to ground, forming a first-order RC low-pass filter to prevent high-frequency interference signals from entering the differential input terminal of the processing chip 8. The TEMP pin integrated into the processing chip 8 for temperature detection is electrically connected to the positive current port. The processing chip 8 detects the voltage on the TEMP pin, converts it to the current temperature value, and performs digital compensation for zero-point / full-scale temperature drift internally. This part of the circuit is directly connected to the I+ terminal (i.e., the positive power supply terminal of the sensor bridge), requiring no external components.

[0023] After receiving a signal, the processing chip 8 amplifies it through a signal amplification circuit. The signal amplification module 9 includes an output transistor Q2. The output pin of the processing chip 8 is connected to the base of Q2 through a resistor R3, and simultaneously connected between the base and collector of Q2 through a capacitor C5. The collector of Q2 is electrically connected to the protection module 10 after being stepped down by resistors R4 and R5. The signal amplification module also includes capacitor C4, resistor R2, and capacitor C3. The processing chip 8 also includes an OWI pin, an FBN pin, and a Fil pin. One end of capacitor C4 is connected to the Fil pin for filtering, and the other end is grounded. One end of resistor R2 is connected to the OWI pin for current limiting, and the other end is connected to the protection module 10 through capacitor C3.

[0024] In the output transistor Q2, the OUT pin outputs a DC voltage proportional to the pressure. After being current-limited by R3, this voltage is applied to the base and emitter of Q2. The capacitor C5 connected across the emitter feeds back the high-frequency changes of the electrodes to the base, suppressing high-frequency oscillations and ensuring stable amplification. To prevent interference signals from entering the internal digital circuitry of the chip via the OWI pin, C3 is used as a bypass capacitor to provide a high-frequency return path to the OWI pin, reducing transient overshoot and ringing on the pin.

[0025] The protection module 10 includes multiple capacitors connected to the signal amplification module 9 to couple high-frequency transient noise on the collector of Q2 to the bidirectional TVS diode D3 for output after low-frequency decoupling and intermediate-frequency filtering of Q2. The protection module 10 includes capacitors C0, C16, and C14, a high-frequency filter bead B1, and a high-frequency filter bead B2. The two ends of capacitor C0 are connected to the emitter and collector of Q2 respectively. The two ends of capacitor C16 are connected to capacitor C3 and the collector of Q2 respectively. One end of the high-frequency filter bead B1 is connected to the chassis ground through capacitor C14, and the other end is connected to the bidirectional TVS diode D3. One end of the high-frequency filter bead B2 is connected to the chassis ground through capacitor C15, and the other end is connected to the bidirectional TVS diode D3.

[0026] In protection module 10, capacitor C0 is connected across the collector and emitter of Q2 to smooth collector voltage fluctuations and filter low frequencies. Capacitors C13 and C14 couple high-frequency components from lightning strikes / surges on the collector of Q2 to the protection link; their 1000V withstand voltage ensures they will not break down or short-circuit under high-voltage impacts. Capacitor C16 bypasses high-frequency common-mode noise coupled to the OWI pin communication line to loop ground Io, preventing interference from affecting the analog circuit through the digital ground loop.

[0027] An external power supply also includes a bidirectional TVS diode D4, and a varistor R0 is connected in series between D3 and D4. R0 acts as a varistor, providing surge energy diversion, clamping voltage matching, and high-frequency oscillation suppression between D3 and D4. This allows the common-mode D3 and differential-mode D4 protection paths to work together during a surge, preventing a single TVS diode from bearing all the energy and improving the overall reliability and surge tolerance of the protection network.

[0028] Similarly, the small-range high-precision differential pressure transmitter, including the aforementioned small-range high-precision differential pressure transmitter, is also within the protection scope of this invention. In actual design, the measuring device includes a housing 6, which is divided into upper and lower layers and connected by fixing screws 1 to protect the internal sensors and circuits. The top of the housing 6 integrates a port connector 3 for electrical connection to the processing chip 8. The bottom of the housing 6 has an air nozzle 4 for connecting to an external air pipe. The top surface of the housing 6 also integrates a display screen 2. The display screen 2 is integrated with the small-range high-precision differential pressure transmitter through a microcontroller. The microcontroller model is HC32L136J8TA. After the display circuit is integrated, it can be zeroed by one-click operation via the zeroing button 5.

[0029] In this invention, the pressure signal is powered by the processing chip 8, which converts the resistance signal of the differential pressure sensor into a voltage signal for acquisition. After A / D conversion and calibration, it is finally converted into a current signal and output. In the field of ultra-small range micro differential pressure measurement, this invention effectively solves the long-standing contradictions between "high precision retention limited by temperature drift", "on-site debugging convenience limited by physical interface", and "installation adaptability limited by mechanical stress".

Claims

1. A small-range, high-precision differential pressure transmitter, characterized in that, include: The system comprises a signal input module, a processing chip, a signal amplification module, and a protection module. An external power supply is electrically connected to the processing chip to power the signal input module. The signal input module electrically connects an external differential pressure sensor to the processing chip. The output port of the processing chip is electrically connected to the signal amplification module, which is also electrically connected to the protection module. The signal amplification module includes an output transistor Q2. The output pin of the processing chip is connected to the base of Q2 via resistor R3, and simultaneously connected between the base and collector of Q2 via capacitor C5. The collector of Q2 is electrically connected to the protection module after being stepped down by resistors R4 and R5. The protection module includes multiple capacitors connected to the signal amplification module to couple high-frequency transient noise on the collector of Q2 to a bidirectional TVS diode D3 for output after low-frequency decoupling and intermediate-frequency filtering. The terminal interfaces in the signal input module include positive / negative current ports and positive / negative differential signal ports. The positive / negative current ports are connected to IEXC1 of the processing chip. The positive / negative differential signal ports are connected to the VIP and VIN pins of the processing chip, respectively. The positive / negative differential signal ports are also grounded via capacitors C6 and C7 for filtering. The processing chip also integrates a TEMP pin for temperature detection, which is electrically connected to the positive current port. The signal amplification module further includes capacitor C4, resistor R2, and capacitor C3. The processing chip also includes an OWI pin, an FBN pin, and a Fil pin. One end of capacitor C4 is connected to the Fil pin for filtering, and the other end is grounded. One end of resistor R2 is connected to the OWI pin for current limiting, and the other end is connected to the protection module via capacitor C3.

2. The small-range, high-precision differential pressure transmitter according to claim 1, characterized in that: The protection module includes capacitors C0, C16, and C14, a high-frequency filter bead B1, and a high-frequency filter bead B2. The two ends of capacitor C0 are connected to the emitter and collector of Q2, respectively. The two ends of capacitor C16 are connected to capacitor C3 and the collector of Q2, respectively. One end of high-frequency filter bead B1 is connected to the chassis ground through capacitor C14, and the other end is connected to the bidirectional TVS diode D3. One end of high-frequency filter bead B2 is connected to the chassis ground through capacitor C15, and the other end is connected to the bidirectional TVS diode D3.

3. A small-range, high-precision differential pressure transmitter according to claim 2, characterized in that: A bidirectional TVS diode D4 is connected to the external power supply, and a varistor R0 is connected in series between D3 and D4.

4. A small-range, high-precision differential pressure transmitter according to claim 1, characterized in that: The differential pressure sensor is model SSCL04DF.

5. A small-range, high-precision differential pressure transmitter according to claim 1, characterized in that: The processing chip is model NSA2862.

6. A small-range, high-precision differential pressure transmitter according to claim 1, characterized in that: It also includes a housing, which is divided into upper and lower layers and connected by fixing screws. The top of the housing has an integrated port connector for electrical connection to the processing chip, and the bottom of the housing has an air nozzle for connection to an external air pipe.

7. A small-range, high-precision differential pressure transmitter according to claim 6, characterized in that: The top surface of the housing is also integrated with a display screen, which is integrated with the small-range high-precision differential pressure transmitter via a microcontroller, the microcontroller model being HC32L136J8TA.

Images