Indirect temperature compensation RS485 digital pressure transmitter

Abstract

The utility model provides an indirect temperature compensation RS485 digital pressure transmitter, and relates to the technical field of pressure measurement. The transmitter comprises a pressure sensing module, an intelligent sensor conditioning compensation module and a signal conversion module. The pressure sensing module comprises a silicon piezoresistive sensor chip, a built-in temperature sensor and an all-welded stainless steel isolating membrane structure, the silicon piezoresistive sensor chip is welded to the bottom face of an inner cavity of the all-welded stainless steel isolating membrane structure, and the built-in temperature sensor is attached to the back face of a substrate of the silicon piezoresistive sensor chip. The intelligent sensor conditioning compensation module comprises an I2C conditioning chip provided with a temperature compensation circuit, and the input end of the I2C conditioning chip is connected with pins of the silicon piezoresistive sensor chip and the built-in temperature sensor. The signal conversion module comprises an I2C to RS485 circuit, and the input end of the signal conversion module is connected with an SDA / SCL pin of the I2C conditioning chip. According to the transmitter, the problem of inaccurate temperature compensation caused by the structural design of a traditional transmitter is solved, and the pressure measurement precision of the whole temperature zone is remarkably improved.

Description

Technical Field

[0001] This utility model relates to the field of pressure measurement technology, and more specifically, to an indirect temperature-compensated RS485 digital pressure transmitter. Background Technology

[0002] Currently, RS485 digital pressure transmitters generally adopt a split structure design, with the sensor chip and temperature sensor physically separated, resulting in a lag in temperature compensation signal acquisition. At the same time, the traditional isolation diaphragm structure is susceptible to thermal stress deformation in a wide temperature environment due to insufficient welding sealing, causing significant temperature drift of the pressure signal and making it difficult to achieve accurate compensation across the entire temperature range.

[0003] Existing technologies, which separate the external temperature compensation circuit from the sensor, can partially alleviate the temperature drift problem. However, the discrete components lead to circuit redundancy and complex calibration. Furthermore, the compensation accuracy is limited by the physical distance between the sensor and the temperature probe, making it impossible to achieve chip-level synchronous temperature acquisition and real-time compensation.

[0004] In conclusion, solving the problem of inaccurate temperature compensation caused by the traditional transmitter structural design is an urgent issue that needs to be addressed. Utility Model Content

[0005] The main purpose of this invention is to provide an indirect temperature-compensated RS485 digital pressure transmitter, which at least solves the problem of inaccurate temperature compensation caused by the structural design of traditional transmitters, significantly improves the pressure measurement accuracy across the entire temperature range, and simplifies the circuit layout and enhances adaptability to harsh environments.

[0006] To achieve the above objectives, this utility model provides an indirect temperature-compensated RS485 digital pressure transmitter, the transmitter comprising:

[0007] Pressure sensing module, intelligent sensor conditioning and compensation module and signal conversion module;

[0008] The pressure sensing module includes a silicon piezoresistive sensor chip, a built-in temperature sensor, and a fully welded stainless steel isolation membrane structure. The silicon piezoresistive sensor chip is fixed to the bottom surface of the inner cavity of the fully welded stainless steel isolation membrane structure by pin welding, and the built-in temperature sensor is attached to the back of the substrate of the silicon piezoresistive sensor chip.

[0009] The intelligent sensor conditioning and compensation module includes an I2C conditioning chip with a temperature compensation circuit. The input terminal of the I2C conditioning chip is connected to the pins of the silicon piezoresistive sensor chip and the built-in temperature sensor.

[0010] The signal conversion module includes an I2C to RS485 circuit, and the input terminal of the I2C to RS485 circuit is connected to the SDA / SCL pin of the I2C conditioning chip.

[0011] Specifically, the fully welded stainless steel isolation membrane structure consists of two layers of 316L stainless steel membrane sheets that are laser-welded to form a sealed inner cavity. The silicon piezoresistive sensor chip and the built-in temperature sensor are fixed in the inner cavity with epoxy resin sealant.

[0012] Specifically, the I2C conditioning chip also includes a linearization processing circuit;

[0013] The input terminal of the linearization processing circuit is connected to the output terminal of the silicon piezoresistive sensor chip, and the output terminal of the linearization processing circuit is connected to the compensation parameter storage pin of the I2C conditioning chip.

[0014] Specifically, the signal conversion module further includes a surge protection circuit, which is connected in series with the RS485 signal output terminal of the I2C to RS485 circuit.

[0015] Specifically, the pressure sensing module, the intelligent sensor conditioning and compensation module, and the signal conversion module are packaged into an integrated structure, and the operating temperature range of the integrated structure is -40℃ to 85℃.

[0016] This invention provides an indirect temperature-compensated RS485 digital pressure transmitter, comprising a pressure sensing module, an intelligent sensor conditioning and compensation module, and a signal conversion module. The pressure sensing module includes a silicon piezoresistive sensor chip, a built-in temperature sensor, and a fully welded stainless steel diaphragm structure. The silicon piezoresistive sensor chip is welded to the bottom surface of the inner cavity of the fully welded stainless steel diaphragm structure, and the built-in temperature sensor is mounted on the back of the substrate of the silicon piezoresistive sensor chip. The intelligent sensor conditioning and compensation module includes an I2C conditioning chip with a temperature compensation circuit; its input is connected to the pins of the silicon piezoresistive sensor chip and the built-in temperature sensor. The signal conversion module includes an I2C to RS485 converter circuit; its input is connected to the SDA / SCL pins of the I2C conditioning chip, realizing signal conversion and transmission. This transmitter solves the problem of inaccurate temperature compensation caused by the traditional transmitter design, significantly improving the pressure measurement accuracy across the entire temperature range. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0018] Figure 1 This is a cross-sectional schematic diagram of an optional indirect temperature-compensated RS485 digital pressure transmitter according to an embodiment of the present utility model.

[0019] 10. Pressure sensing module; 11. Silicon piezoresistive sensor chip; 12. All-welded stainless steel isolation diaphragm structure; 13. Built-in temperature sensor; 20. Intelligent sensor conditioning and compensation module; 21. I2C conditioning chip; 30. Signal conversion module; 31. I2C to RS485 circuit; 32. Surge protection circuit. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] An indirect temperature-compensated RS485 digital pressure transmitter according to an embodiment of this utility model, such as... Figure 1 As shown, this utility model provides an indirect temperature-compensated RS485 digital pressure transmitter, which includes: a pressure sensing module 10, an intelligent sensor conditioning and compensation module 20, and a signal conversion module 30. The pressure sensing module 10 includes a silicon piezoresistive sensor chip 11, a built-in temperature sensor 13, and a fully welded stainless steel isolation diaphragm structure 12. The silicon piezoresistive sensor chip 11 is fixed to the bottom surface of the inner cavity of the fully welded stainless steel isolation diaphragm structure 12 by pin welding. The built-in temperature sensor 13 is attached to the back of the substrate of the silicon piezoresistive sensor chip 11. The intelligent sensor conditioning and compensation module 20 includes an I2C conditioning chip 21 with a temperature compensation circuit. The input terminal of the I2C conditioning chip 21 is connected to the pins of the silicon piezoresistive sensor chip 11 and the built-in temperature sensor 13. The signal conversion module 30 includes an I2C to RS485 circuit 31. The input terminal of the I2C to RS485 circuit 31 is connected to the SDA / SCL pin of the I2C conditioning chip 21. Specifically, the indirect temperature-compensated RS485 digital pressure transmitter provided in this embodiment is implemented as follows:

[0022] 1. Structure and connection of pressure sensing module 10

[0023] The pressure sensing module 10 includes a silicon piezoresistive sensor chip 11, a built-in temperature sensor 13, and a fully welded stainless steel isolation diaphragm structure 12. The fully welded stainless steel isolation diaphragm structure 12 is a cylindrical cavity structure filled with silicone oil. A stainless steel diaphragm is sealed to the cavity using laser welding, forming a corrosion-resistant and overload-resistant isolation cavity. The silicon piezoresistive sensor chip 11 is welded to the bottom surface of the inner cavity of the fully welded stainless steel isolation diaphragm structure 12 using a tin-lead solder layer, ensuring that the pressure-sensing surface of the silicon piezoresistive sensor chip 11 is in contact with the inner side of the stainless steel diaphragm, transmitting external pressure to the pressure-sensing surface through the silicone oil. The built-in temperature sensor 13 is a surface-mount PT100 platinum resistance thermometer, mounted on the back of the ceramic substrate of the silicon piezoresistive sensor chip 11 using thermally conductive adhesive, directly monitoring the substrate temperature of the silicon piezoresistive sensor chip 11.

[0024] 2. Circuit configuration of the intelligent sensor conditioning and compensation module 20

[0025] The intelligent sensor conditioning and compensation module 20 includes an I2C conditioning chip 21 with a temperature compensation circuit. The analog input of the I2C conditioning chip 21 is connected to the Wheatstone bridge output pin of the silicon piezoresistive sensor chip 11 via gold wire bonding, and the digital input is connected to the pin of the built-in temperature sensor 13 via copper wires. The temperature compensation circuit uses a polynomial fitting algorithm to perform nonlinear correction on the pressure signal output by the silicon piezoresistive sensor chip 11 and the temperature signal acquired by the built-in temperature sensor 13, generating a compensated digital pressure signal and outputting it via the I2C protocol.

[0026] 3. Circuit implementation of signal conversion module 30

[0027] The signal conversion module 30 includes an I2C to RS485 circuit 31. The input of the I2C to RS485 circuit 31 is connected to the SDA and SCL pins of the I2C conditioning chip 21 via copper traces on the PCB board. It uses differential signal transmission to convert the digital pressure signal of the I2C protocol into a standard RS485 signal and outputs it to an external device through the RS485 interface. The I2C to RS485 circuit 31 incorporates surge protection and electromagnetic isolation devices to suppress external electromagnetic interference.

[0028] 4. Physical layout and function between modules

[0029] The outer surface of the all-welded stainless steel isolation membrane structure 12 is made of 316L stainless steel and is connected to external pipelines through welding to ensure sealing and resistance to mechanical shock. The Wheatstone bridge output signal of the silicon piezoresistive sensor chip 11 is temperature-compensated by the I2C conditioning chip 21 to eliminate zero-point drift and sensitivity errors caused by ambient temperature changes, improving pressure measurement accuracy across the entire temperature range of -40℃ to 125℃. The differential signal transmission method of the I2C to RS485 circuit 31 enhances signal stability over long distances and in noisy industrial environments, and is compatible with the RS485 bus communication protocol.

[0030] In summary, this transmitter solves the problem of inaccurate temperature compensation caused by the structural design of traditional transmitters, significantly improves the pressure measurement accuracy across the entire temperature range, and simplifies the circuit layout while enhancing adaptability to harsh environments.

[0031] The following are preferred specific embodiments:

[0032] Specifically, the all-welded stainless steel isolation membrane structure 12 is formed by laser welding of two layers of 316L stainless steel membrane sheets to form a sealed inner cavity, and the silicon piezoresistive sensor chip 11 and the built-in temperature sensor 13 are fixed in the inner cavity with epoxy resin sealant.

[0033] Specifically, the I2C conditioning chip 21 is further provided with a linearization processing circuit;

[0034] The input terminal of the linearization processing circuit is connected to the output terminal of the silicon piezoresistive sensor chip 11, and the output terminal of the linearization processing circuit is connected to the compensation parameter storage pin of the I2C conditioning chip 21.

[0035] Specifically, the signal conversion module 30 further includes a surge protection circuit 32, which is connected in series with the RS485 signal output terminal of the I2C to RS485 circuit 31.

[0036] Specifically, the pressure sensing module 10, the intelligent sensor conditioning and compensation module 20, and the signal conversion module 30 are packaged into an integrated structure, and the operating temperature range of the integrated structure is -40℃ to 85℃.

[0037] This embodiment also provides a preferred implementation of an indirect temperature-compensated RS485 digital pressure transmitter, the specific technical solution of which is as follows:

[0038] 1. Detailed structure and connection of pressure sensing module 10

[0039] The pressure sensing module 10 includes a silicon piezoresistive sensor chip 11, a built-in temperature sensor 13, and a fully welded stainless steel isolation membrane structure 12. The fully welded stainless steel isolation membrane structure 12 consists of two layers of 316L stainless steel diaphragms laser-welded to form a sealed inner cavity, which is filled with silicone oil. The edges of the upper and lower diaphragms are sealed with continuous annular laser welds. The silicon piezoresistive sensor chip 11 and the built-in temperature sensor 13 are fixed in the inner cavity using epoxy resin sealant: the silicon piezoresistive sensor chip 11 is bonded to the center of the inner surface of the lower stainless steel diaphragm using epoxy resin sealant, and the built-in temperature sensor 13 is attached to the back of the ceramic substrate of the silicon piezoresistive sensor chip 11 using epoxy resin sealant. The cured epoxy resin sealant has a thickness of 0.1 mm, forming a shock-resistant and media-proof fixing layer after curing.

[0040] 2. Circuit expansion of the intelligent sensor conditioning and compensation module 20

[0041] The intelligent sensor conditioning and compensation module 20 includes an I2C conditioning chip 21 equipped with a temperature compensation circuit and a linearization processing circuit. The temperature compensation circuit uses a polynomial fitting algorithm to perform nonlinear correction between the Wheatstone bridge output signal of the silicon piezoresistive sensor chip 11 and the platinum resistance temperature signal of the built-in temperature sensor 13. The input terminal of the linearization processing circuit is connected to the output pin of the silicon piezoresistive sensor chip 11 via gold wire bonding, and the output terminal is connected to the compensation parameter storage pin of the I2C conditioning chip 21 via copper wire. The linearization processing circuit uses a piecewise linear correction algorithm to perform slope piecewise calibration on the nonlinear pressure signal output by the silicon piezoresistive sensor chip 11, eliminating sensitivity deviation.

[0042] 3. Enhanced protection circuitry for signal conversion module 30

[0043] The signal conversion module 30 includes an I2C to RS485 circuit 31 and a surge protection circuit 32. The input terminal of the I2C to RS485 circuit 31 is connected to the SDA and SCL pins of the I2C conditioning chip 21 via copper traces on the PCB board, and the output terminal is connected in series with the surge protection circuit 32 via copper wires. The surge protection circuit 32 is composed of a TVS diode and a gas discharge tube connected in parallel. The clamping voltage of the TVS diode is 24V, and the breakdown voltage of the gas discharge tube is 90V. The two are connected in parallel to the RS485 signal output terminal to suppress transient overvoltage and lightning surges.

[0044] 4. Integrated packaging structure and temperature range adaptation

[0045] The pressure sensing module 10, the intelligent sensor conditioning and compensation module 20, and the signal conversion module 30 are encapsulated into an integrated structure within an aluminum alloy housing. The inner wall of the aluminum alloy housing is coated with an epoxy resin insulating layer, and the internal circuitry is fixed by silicone gel potting. The integrated structure operates within a temperature range of -40℃ to 85℃. A laser welding process with matched thermal expansion coefficients is used during encapsulation to ensure that the housing and stainless steel diaphragm do not experience stress deformation under temperature changes.

[0046] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An indirect temperature-compensated RS485 digital pressure transmitter, characterized in that, include: Pressure sensing module (10), intelligent sensor conditioning and compensation module (20) and signal conversion module (30); The pressure sensing module (10) includes a silicon piezoresistive sensor chip (11), a built-in temperature sensor (13), and a fully welded stainless steel isolation membrane structure (12). The silicon piezoresistive sensor chip (11) is fixed to the bottom surface of the inner cavity of the fully welded stainless steel isolation membrane structure (12) by pin welding. The built-in temperature sensor (13) is attached to the back of the substrate of the silicon piezoresistive sensor chip (11). The intelligent sensor conditioning and compensation module (20) includes an I2C conditioning chip (21) with a temperature compensation circuit. The input terminal of the I2C conditioning chip (21) is connected to the pins of the silicon piezoresistive sensor chip (11) and the built-in temperature sensor (13). The signal conversion module (30) includes an I2C to RS485 circuit (31), the input terminal of which is connected to the SDA / SCL pin of the I2C conditioning chip (21).

2. The indirect temperature-compensated RS485 digital pressure transmitter according to claim 1, characterized in that, The fully welded stainless steel isolation membrane structure (12) is formed by laser welding of two layers of 316L stainless steel membranes to form a sealed inner cavity. The silicon piezoresistive sensor chip (11) and the built-in temperature sensor (13) are fixed in the inner cavity by epoxy resin sealant.

3. The indirect temperature-compensated RS485 digital pressure transmitter according to claim 1, characterized in that, The I2C conditioning chip (21) is also provided with a linearization processing circuit; The input terminal of the linearization processing circuit is connected to the output terminal of the silicon piezoresistive sensor chip (11), and the output terminal of the linearization processing circuit is connected to the compensation parameter storage pin of the I2C conditioning chip (21).

4. The indirect temperature-compensated RS485 digital pressure transmitter according to claim 1, characterized in that, The signal conversion module (30) also includes a surge protection circuit (32), which is connected in series with the RS485 signal output terminal of the I2C to RS485 circuit (31).

5. The indirect temperature-compensated RS485 digital pressure transmitter according to claim 1, characterized in that, The pressure sensing module (10), the intelligent sensor conditioning and compensation module (20), and the signal conversion module (30) are packaged as an integrated structure, and the operating temperature range of the integrated structure is -40℃ to 85℃.

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