CN214588054U - Digital pressure transmitter - Google Patents

Abstract

The utility model discloses a digital pressure transmitter, including sense terminal casing, automatically controlled casing, signal connector, power connector, automatically controlled casing is the columnar body, install the lateral wall of automatically controlled casing signal connector, power connector, the one end of columnar body is equipped with the housing end cover, the columnar body other end is installed through sensor connecting portion the sense terminal casing. The shell structure is designed in a partitioning mode, circuit design is improved, digital circuit processing is adopted, analog quantity processing of the digital circuit is completed through programs, the problems can be solved as long as programming is carried out, the structure is simple, debugging is convenient, and the requirement for signal fidelity can be met.

Description

Digital pressure transmitter

Technical Field

The utility model belongs to the technical field of pressure transmitter technique and specifically relates to a digital pressure transmitter.

Background

In the nuclear industry, due to the problems of nuclear radiation, irradiation and the like, all adopted instruments adopt nuclear-grade equipment, and the nuclear-grade equipment is designed during design and installation so as to prolong the service life of the nuclear-grade equipment. For example, some conventional transmitters fail to meet nuclear-grade requirements during differential pressure sensing. When people send a conventional transmitter into a nuclear reaction plant area for detection test, the problems that the equipment has function failure or detection precision deviation and the like in a short service cycle are found. Due to the fact that faults occur, equipment is replaced and installed, and due to the fact that the equipment belongs to the nuclear industry, radiation can exist in all operations, and life safety of people is threatened. The transmitter circuitry consists of a load cell sensor (also known as a pressure sensor), measurement processing circuitry, and process connections. The pressure sensor can convert the physical pressure parameter of the liquid sensed by the pressure element sensor into a standard electric signal to be supplied to secondary instruments such as an indication alarm instrument, a recorder and a regulator for measurement, indication and process regulation.

The circuit of the prior art nuclear pressure transmitter is analog, and can only represent the measured value through the output current, and can not provide other information (such as instrument state, fault information and the like); the calibration process is complex by adopting an analog circuit, and the calibration can be realized by repeatedly adjusting for many times; the digital communication function cannot be realized, and the configuration cannot be realized.

SUMMERY OF THE UTILITY MODEL

The utility model provides a digital pressure transmitter to the demand that the nuclear industry protected against radiation, through carrying out the partition design to the shell structure, improves circuit design, adopts the digital integrated circuit of anti-irradiation to handle, simple structure, and debugging and calibration are convenient, and measurement accuracy is higher, can realize more functions. Meanwhile, reasonable adjustment and optimization are carried out on the structural design in order to improve the anti-interference capability.

In order to achieve the above purpose, the utility model adopts the following specific technical scheme:

further described, a digital pressure transmitter, the key of which is: the detection end comprises a detection end shell, an electric control shell, a signal connector and a power connector, wherein the electric control shell is a cylindrical body, the signal connector and the power connector are mounted on the side wall of the electric control shell, a shell end cover is arranged at one end of the cylindrical body, and the detection end shell is mounted at the other end of the cylindrical body through a sensor connecting part;

a circuit board cavity is arranged in the electric control shell and is provided with a power module, an MCU processing circuit, a D/A conversion circuit, a voltage/current conversion circuit, an RS422 communication processing circuit, a storage circuit, a temperature measuring circuit and a detection acquisition circuit;

the power supply module comprises a power supply conversion circuit, a power supply output circuit and a power supply input circuit;

the temperature measuring circuit detects temperature signals and transmits the temperature signals to the MCU processing circuit, the MCU processing circuit is connected with the storage circuit, the MCU processing circuit is connected with the D/A conversion circuit, the D/A conversion circuit is connected with the voltage/current conversion circuit, the voltage/current conversion circuit is connected with an interface of the power input circuit and is connected with the power connector, the MCU processing circuit is connected with the RS422 communication processing circuit, and the RS422 communication processing circuit is connected with the signal connector.

By adopting the scheme, the two connectors are respectively used for power supply and signal transmission, and the circuit is processed by a digital circuit and is externally output through the signal connectors. The digital circuit can be more flexible than the analog circuit without changing the circuit structure or only adding some standard auxiliary processing units.

Further, the circuit board cavity is sealed in the electric control shell through the shell end cover, the electric control shell and the detection end shell are connected through a tee welding sleeve, a signal line via hole is formed in the tee welding sleeve, one end of the signal line via hole is communicated with the detection end shell, the other end of the signal line via hole is communicated with a wire harness hole in the electric control shell, and the wire harness hole is communicated with the circuit board cavity;

the sensor is installed in the detection end shell, and the detection end shell is provided with a detection hole.

Adopt above-mentioned scheme, the subregion structure can not cause circuit element's the influence of each other, adopts neotype structure, arranges the sensor in the sensor cavity inside, obtains pressure difference signal through a plurality of inspection holes, and this pressure difference signal is handled through signal conversion circuit and is sent into the circuit board cavity of automatically controlled casing by the inspection signal input hole.

Further, the other end of the cylindrical body is provided with a meter cylinder bottom plate, and the lateral wall of the cylindrical body forms a meter head shell;

the gauge outfit shell barrel, the outer wall of the wire harness hole and the gauge barrel bottom plate form a shielding chamber in an enclosing mode;

at least 2 signal line through holes are formed in the partition boards of the circuit board cavity and the shielding cavity, at least 2 internal signal line passing heads are arranged on the signal line through holes, and the internal signal line passing heads extend into the shielding cavity;

the shielding cavity is communicated with the signal output hole, the signal line via holes and the signal output hole are arranged in a staggered mode, and the signal line via holes form an anti-radiation channel through a line channel of the shielding cavity and the signal output hole;

the meter cylinder bottom plate is provided with a sensor connecting part through hole, and the meter cylinder bottom plate is welded with the meter head shell cylinder.

By adopting the scheme, the detection part, the signal conversion part and the signal output part are designed into chambers and are independent, and the signal line via holes and the signal output holes are arranged in a staggered manner to form the anti-radiation dense channel. The circuit board and the electronic component adopt anti-irradiation boards and devices, so that interference caused by irradiation is effectively prevented.

As further described, two opposite end portions of the three-way welding sleeve are respectively provided with a sleeve cover, the two sleeve covers are respectively provided with one detection hole, and the two detection holes are symmetrically arranged;

the sensor connecting part of the electric control shell is connected with the vertical end part of the three-way welding sleeve, and a switching circuit board chamber is formed by the vertical end part of the three-way welding sleeve in a surrounding manner; the switching circuit board chamber is internally provided with a switching circuit board which is provided with a signal switching circuit.

The signal connector comprises a signal aviation socket base, a signal connector socket and a signal connector plug which are connected in sequence;

the power connector also comprises a power aviation socket base, a power connector socket and a power connector plug which are connected in sequence.

By adopting the scheme, the chambers are arranged in different areas, different circuit boards are placed to prevent mutual interference, a plurality of detection holes are formed, and the detection effectiveness is increased.

Further, the chip U5 of the temperature measuring circuit is an AD conversion chip and adopts parallel port output;

u14 in the D/A conversion circuit is a D/A conversion chip, chips U13 and U15 are used for port expansion, and the models of the chips U13 and U14 are both B54AC 373;

the internal part of the reference voltage of the REFLO _ AD + GND is 2.5V, and the external part of the reference voltage of the REFLO _ AD + VDDA is 2.5V;

the detection signal input part adopts an AD sampling circuit, and the signal plate converts a pressure signal into parallel port data through AD and inputs the parallel port data.

The MCU processing circuit adopts an 80C32E singlechip, and the MCU processing circuit and the storage circuit both adopt anti-radiation circuits;

a chip U33 in the RS422 communication processing circuit is a transmitting circuit, and the model of the chip U33 is B26C31, so that data transmitted by the MCU from the TXD are converted into differential output signals of T + and T-;

a chip U34 in the RS422 communication processing circuit is a receiving circuit, and the chip model B26C32 converts differential signals received from R + and R-into level signals RXD and is connected to the MCU;

the voltage/current conversion circuit is used for inputting a voltage signal output by the D/A conversion circuit into the voltage/current conversion circuit through a resistor R107 in the voltage/current conversion circuit, and converting the voltage signal into a current signal of 4-20mA through an operational amplifier.

Three external interfaces which are respectively a communication interface, a power input interface and a 4-20mA current output interface are led out of the cavity of the circuit board;

the communication interface is arranged on the signal connector, and the signal connector is communicated with the RS422 communication processing circuit;

the power input interface and the 4-20mA current output interface are connected to the power connector.

By adopting the scheme, the output of the direct-current voltage signal of 0-5V can be directly matched with the input voltage of a target. But the transmission distance of the constant voltage source output mode is short. The transmission line partial pressure has the error and can not discover the abnormal reason of changer in time. Therefore, in recent years, the transmitter gradually adopts a 4-20mA constant current source output mode. When the output current is less than 4 mA. Transmitter or loop anomalies can be determined.

Further, the voltage/current conversion circuit includes an operational amplifier U36, an operational amplifier U37, a transistor Q5, a transistor Q6, and an interface J5;

a positive input end 3 of the operational amplifier U37 is connected with one end of a resistor R107, the other end of the resistor R107 serves as an IOUTA1 end and is used for connecting the D/a conversion circuit, the positive input end 3 of the operational amplifier U37 is further grounded through a capacitor C96, a power supply end 7 of the operational amplifier U37 is connected with VCC12V +, a ground end 4 of the operational amplifier U37 is connected with VCC12V-, a zero adjustment end 1 of the operational amplifier U37 is connected with a zero adjustment end 8 of the operational amplifier U37 through a rheostat RPot1, an output end 6 of the operational amplifier U37 is connected with the positive input end 3 of the operational amplifier U36 through a resistor R103, a resistor R100 and a resistor R101, a common end of the resistor R103 and the resistor R100 is further grounded through a capacitor C95, a common end of the resistor R103 and the resistor R100 is further connected with an anode of a diode D17 through a resistor R104, and a common end of the resistor R100 and the resistor R101 is connected with an anode of the diode D17 through an anode of the diode D91, a forward input end 3 of the operational amplifier U36 is grounded via a capacitor C94, a reverse input end 2 of the operational amplifier U36 is connected to an output end 6 of the operational amplifier U36 via a capacitor C93, a zeroing end 1 of the operational amplifier U36 is connected to a zeroing end 8 of the operational amplifier U37 via a rheostat RPot2, a power supply end 7 of the operational amplifier U36 is connected to VCC12V +, a ground end 4 of the operational amplifier U36 is connected to VCC12V-, the output end 6 of the operational amplifier U36 is connected to a base of the triode Q5 via a resistor R102, the output end 6 of the operational amplifier U36 is connected to a collector of the triode Q5 and a collector of the triode Q6 via a resistor R102, a resistor R99 and a capacitor C89, respectively, an emitter of the triode Q5 is connected to the base of the triode Q6, an emitter of the triode Q6 is grounded via a resistor R106, and a collector of the triode Q5 is grounded via a capacitor C92, the collector electrode of the triode Q5 is connected with the anode of a diode D17 through a capacitor C92 and a rod-shaped resistor R108 in sequence, the cathode of the diode D17 is connected with the 2 end of the interface J5, the 1 end of the interface J5 is connected with the collector electrode of the triode Q5 and the common end of the collector electrode of the triode Q6, a capacitor C90 is connected between the 1 end and the 2 end of the interface J5 in parallel, and the interface J5 is used as the 4-20mA current output interface.

The utility model has the advantages that: aiming at the radiation protection requirement of the nuclear industry, the shell structure is designed, most parts of detection, signal conversion and signal output of the differential pressure transmitter are partitioned, and a cavity is correspondingly set for circuit arrangement. These advantages of digital circuits are more prominent with respect to a large number and variety of signal processing. The digital circuit is easier to standardize, and the greatest benefit is that the cost is sharply reduced, and the time for constructing the circuit is greatly shortened. The detection, conversion and output of the signals are completed through the processing of the multi-stage circuit. The current signal output can be adopted to reduce errors and find the abnormal reason of the transmitter. Meanwhile, aiming at the nuclear grade requirement, a control circuit board cavity for preventing irradiation is reserved and used for installing a lead box for preventing irradiation. The function is divided, the design is precise, and the sealing effect is good.

Drawings

Fig. 1 is a perspective view of the present invention;

fig. 2 is a right side view of the present invention;

fig. 3 is a left side view of the present invention;

FIG. 4 is a cross-sectional view A-A of FIG. 3;

fig. 5 is a front view of the present invention;

FIG. 6 is a cross-sectional view C-C of FIG. 5;

fig. 7 is a circuit frame diagram of the present invention;

fig. 8 is a voltage/current conversion circuit diagram of the present invention;

FIG. 9 is a schematic diagram of a port expansion chip according to the present invention;

fig. 10 is a schematic diagram of an AD conversion chip of the present invention;

fig. 11 is a schematic diagram of the RSS communication transceiver chip of the present invention;

fig. 12 is a schematic diagram of the MCU singlechip of the present invention.

Detailed Description

The following provides a more detailed description of the embodiments and the operation of the present invention with reference to the accompanying drawings.

As can be seen from fig. 1, 3 and 6, a digital pressure transmitter is characterized in that: the detection end comprises a detection end shell C, an electric control shell B, a signal connector A and a power connector D, wherein the electric control shell B is a cylindrical body, the signal connector A and the power connector D are installed on the side wall of the electric control shell B, a shell end cover 1 is arranged at one end of the cylindrical body, and the detection end shell C is installed at the other end of the cylindrical body through a sensor connecting part;

a circuit board cavity 3 is arranged in the electric control shell B, and the circuit board cavity 3 is provided with a power module, an MCU processing circuit, a D/A conversion circuit, a voltage/current conversion circuit, an RS422 communication processing circuit, a storage circuit, a temperature measuring circuit and a detection acquisition circuit;

the power supply module comprises a power supply conversion circuit, a power supply output circuit and a power supply input circuit;

detect the acquisition circuit and detect and gather pressure signal after the transmission give MCU processing circuit, the temperature measurement circuit detects temperature signal transmission extremely MCU processing circuit, MCU processing circuit with memory circuit connects, MCU processing circuit connects after handling D/A converting circuit, the conversion back D/A converting circuit connects voltage/current converting circuit, voltage/current converting circuit with the interface connection of power input circuit power connector D MCU processing circuit still with RS422 communication processing circuit connects, RS422 communication connection signal connector A.

As can be seen from fig. 1 and 6, the circuit board chamber 3 is enclosed in an electronic control housing B through a housing end cover 1, the electronic control housing B and a detection end housing C are connected by a three-way welding sleeve 13, a signal line via hole is formed in the three-way welding sleeve 13, one end of the signal line via hole is communicated with the detection end housing C, the other end of the signal line via hole is communicated with a wiring harness hole 6 in the electronic control housing B, and the wiring harness hole 6 is communicated with the circuit board chamber 3;

the sensor is installed in the detection end shell C, and the detection end shell C is provided with a detection hole 12.

As can be seen from fig. 6, the other end of the column is provided with a watch case bottom plate 10, and the side wall of the column forms a watch case 4;

the gauge outfit shell barrel 4, the outer wall of the wire harness hole 6 and the gauge barrel bottom plate 10 enclose a shielding chamber 9;

4 signal line through holes are formed in the partition boards of the circuit board cavity 3 and the shielding cavity 9 and provided with 4 internal signal line passing heads 11 which extend into the shielding cavity 9;

the shielding cavity 9 is communicated with the signal output hole 7, the signal line via holes and the signal output hole 7 are arranged in a staggered mode, and the signal line via holes form an anti-radiation channel through the shielding cavity 9 and a line channel of the signal output hole 7;

sensor connecting part through holes are formed in the panel of the meter cylinder bottom plate 10, and the meter cylinder bottom plate 10 is welded with the meter head shell cylinder 4.

As can be seen from fig. 3, two opposite end portions of the three-way welding sleeve 13 are respectively provided with a sleeve cover, the two sleeve covers are respectively provided with one detection hole 12, and the two detection holes 12 are symmetrically arranged;

the sensor connecting part of the electric control shell B is connected with the vertical end part of the three-way welding sleeve 13, and a switching circuit board chamber 15 is formed by the vertical end part of the three-way welding sleeve 13 in a surrounding manner; the relay circuit board chamber 15 is provided with a relay circuit board 14 therein, and the relay circuit board 14 is provided with a signal conversion circuit.

As can be seen from fig. 1, the signal connector a includes a signal aviation socket base 21A, a signal connector socket 22A and a signal connector plug 23A which are connected in sequence;

as can be seen from fig. 2, the power connector D includes a power aviation socket base 21D, a power connector socket 22D and a power connector plug 23D, which are connected in sequence.

As can be seen from FIG. 11, the chip U33 in the RS422 communication processing circuit is a transmitting circuit, and the chip U33 with the model B26C31 converts the data sent by the MCU from TXD into differential output signals of T +, T-;

a chip U34 in the RS422 communication processing circuit is a receiving circuit, and the chip model B26C32 converts differential signals received from R + and R-into level signals RXD and is connected to the MCU;

as can be seen from fig. 10, the temperature measuring circuit adopts an AD conversion chip U5 and adopts parallel port output;

as can be seen from fig. 9, the D/a conversion circuit employs a D/a conversion chip U14, and the chips U13 and U15 are used for port expansion;

as can be seen from fig. 12, the MCU processing circuit adopts an 80C32E single chip microcomputer U29, and both the MCU processing circuit and the storage circuit adopt anti-radiation circuits;

the voltage/current conversion circuit is used for converting a voltage signal converted by the D/A into a current signal of 4-20mA by inputting the voltage signal into the voltage/current conversion circuit through a resistor R107 and by operational amplification.

As can be seen from fig. 7, three external interfaces, namely a communication interface, a power input interface and a 4-20mA current output interface, are led out from the cavity of the circuit board;

the communication interface is led to the connector socket 22 of the signal connector A of the electric control shell B by an interface in the RS422 communication processing circuit;

the power input interface and the 4-20mA current output interface are connected to the other connector socket 22 of the power connector D.

As can be seen from fig. 8, the voltage/current conversion circuit includes an operational amplifier U36, an operational amplifier U37, a transistor Q5, a transistor Q6, and an interface J5;

the forward input end 3 of the operational amplifier U37 is used as an IOUTA1 end through a resistor R107, the forward input end 3 is grounded through a capacitor C96, a power supply end 7 of the operational amplifier U37 is connected with VCC12V +, a grounding end 4 of the operational amplifier U37 is connected with VCC12V-, a zeroing end 1 of the operational amplifier U37 is connected with a zeroing end 8 of the operational amplifier U37 through a rheostat RPot1, an output end 6 of the operational amplifier U37 is connected with the forward input end 3 of the operational amplifier U36 through a resistor R103, a resistor R100 and a resistor R101, the resistor R103 is grounded through a capacitor C95, the resistor R103 is connected with the anode of a diode D17 through a resistor R104, the common end of the resistor R100 and the resistor R101 is connected with the anode of the diode D17 through a capacitor C91, the resistor R103 is grounded through a resistor R100, a resistor R101 and a capacitor C94, the reverse input end 2 of the operational amplifier U36 is connected with the output end U736 of the operational amplifier U36, the zero setting end 1 of the operational amplifier U36 is connected with the zero setting end 8 of the operational amplifier U37 through a rheostat RPot2, the power supply end 7 of the operational amplifier U36 is connected with VCC12V +, the grounding end 4 of the operational amplifier U36 is connected with VCC12V-, the output end 6 of the operational amplifier U36 is connected with the base of the triode Q5 through a resistor R102, the output end 6 of the operational amplifier U36 is connected with the collector of the triode Q5 and the collector of the triode Q6 through a resistor R102, a resistor R99 and a capacitor C89, the emitter of the triode Q5 is connected with the base of the triode Q6, the emitter of the triode Q6 is connected with the anode of a diode D17 through a resistor R106 and a rod-shaped resistor R108, the cathode of the diode D17 is connected with the 2 end of the interface J5, the 1 end of the interface J5 is connected with the collector of the triode Q5 and the common end of the collector of the triode Q6, the 1 and 2 ends of the interface J5 are connected with a capacitor C90 in parallel.

The working principle is as follows: when the transmitter works, the signal acquisition circuit detects and acquires signal data and transmits the signal data to the single chip microcomputer in the MCU processing circuit through a parallel port, the temperature measurement circuit detects that temperature signals are converted by AD in the temperature measurement circuit, the parallel port outputs the temperature signals to the single chip microcomputer in the MCU processing circuit, and the MCU processing circuit is connected with the RS422 communication processing circuit and is connected with the signal connector through the RS422 communication processing circuit for communication; the other end of the MCU processing circuit transmits the processed signals to the D/A conversion circuit for digital-to-analog conversion, and the converted signals are transmitted to the voltage/current conversion circuit for conversion and then output 4-20mA current.

Claims (8)

1. A digital pressure transmitter, characterized by: the detection end comprises a detection end shell (C), an electric control shell (B), a signal connector (A) and a power connector (D), wherein the electric control shell (B) is a cylindrical body, the signal connector (A) and the power connector (D) are installed on the side wall of the electric control shell (B), a shell end cover (1) is arranged at one end of the cylindrical body, and the detection end shell (C) is installed at the other end of the cylindrical body through a sensor connecting part;

a circuit board cavity (3) is arranged in the electric control shell (B), and the circuit board cavity (3) is provided with a power module, an MCU processing circuit, a D/A conversion circuit, a voltage/current conversion circuit, an RS422 communication processing circuit, a storage circuit, a temperature measuring circuit and a pressure acquisition circuit;

the power supply module comprises a power supply conversion circuit, a power supply output circuit and a power supply input circuit;

the pressure acquisition circuit detects pressure signal and transmits to MCU processing circuit, the temperature measurement circuit detects temperature signal and transmits to MCU processing circuit, MCU processing circuit with memory circuit connects, MCU processing circuit connects D/A converting circuit, D/A converting circuit connects voltage/current converting circuit, voltage/current converting circuit with the interface of power input circuit all is connected power connector (D), MCU processing circuit with RS422 communication processing circuit connects, RS422 communication processing circuit connects signal connector (A).

2. The digital pressure transmitter of claim 1 wherein: the circuit board cavity (3) is sealed in an electric control shell (B) through a shell end cover (1), the electric control shell (B) is connected with a detection end shell (C) through a three-way welding sleeve (13), a signal line via hole is formed in the three-way welding sleeve (13), one end of the signal line via hole is communicated with the detection end shell (C), the other end of the signal line via hole is communicated with a wire harness hole (6) in the electric control shell (B), and the wire harness hole (6) is communicated with the circuit board cavity (3);

the sensor is installed in the detection end shell (C), and the detection end shell (C) is provided with a detection hole (12).

3. The digital pressure transmitter of claim 2 wherein: a meter cylinder bottom plate (10) is arranged at the other end of the cylindrical body, and a meter head shell (4) is formed on the lateral wall of the cylindrical body;

the gauge outfit shell barrel (4), the outer wall of the wire harness hole (6) and the gauge barrel bottom plate (10) enclose a shielding chamber (9);

at least 2 signal line through holes are formed in the partition boards of the circuit board cavity (3) and the shielding cavity (9), at least 2 internal signal line heads (11) are arranged in the signal line through holes, and the internal signal line heads (11) extend into the shielding cavity (9);

the shielding cavity (9) is communicated with the signal output hole (7), the signal line via holes and the signal output hole (7) are arranged in a staggered mode, and the signal line via holes form an anti-radiation channel through the shielding cavity (9) and a line channel of the signal output hole (7);

the meter cylinder bottom plate (10) is provided with a sensor connecting part via hole on the panel, and the meter cylinder bottom plate (10) is welded with the meter head shell cylinder (4).

4. The digital pressure transmitter of claim 2 wherein: two end parts, which are opposite to the three-way welding sleeve (13), are respectively provided with a sleeve cover (18), the two sleeve covers (18) are respectively provided with one detection hole (12), and the two detection holes (12) are symmetrically arranged;

the sensor connecting part of the electric control shell (B) is connected with the vertical end part of the three-way welding sleeve (13), and a transfer circuit board chamber (15) is enclosed by the vertical end part of the three-way welding sleeve (13); the transfer circuit board cavity (15) is internally provided with a transfer circuit board (14), and the transfer circuit board (14) is provided with a signal conversion circuit.

5. The digital pressure transmitter of claim 1 wherein: the signal connector (A) comprises a signal aviation socket base (21A), a signal connector socket (22A) and a signal connector plug (23A) which are connected in sequence;

the power connector (D) comprises a power aviation socket base (21D), a power connector socket (22D) and a power connector plug (23D) which are connected in sequence.

6. The digital pressure transmitter of claim 1 wherein: the MCU processing circuit adopts an 80C32E singlechip, and the MCU processing circuit and the storage circuit both adopt anti-radiation circuits.

7. The digital pressure transmitter of claim 1 wherein: three external interfaces which are respectively a communication interface, a power input interface and a 4-20mA current output interface are led out of the circuit board cavity (3);

the communication interface is arranged on the signal connector (A), and the signal connector (A) is communicated with the RS422 communication processing circuit;

the power input interface and the 4-20mA current output interface are connected to the power connector (D).

8. The digital pressure transmitter of claim 7 wherein: the voltage/current conversion circuit comprises an operational amplifier U36, an operational amplifier U37, a triode Q5, a triode Q6 and an interface J5;

a positive input end 3 of the operational amplifier U37 is connected with one end of a resistor R107, the other end of the resistor R107 serves as an IOUTA1 end and is used for connecting the D/a conversion circuit, the positive input end 3 of the operational amplifier U37 is further grounded through a capacitor C96, a power supply end 7 of the operational amplifier U37 is connected with VCC12V +, a ground end 4 of the operational amplifier U37 is connected with VCC12V-, a zero adjustment end 1 of the operational amplifier U37 is connected with a zero adjustment end 8 of the operational amplifier U37 through a rheostat RPot1, an output end 6 of the operational amplifier U37 is connected with the positive input end 3 of the operational amplifier U36 through a resistor R103, a resistor R100 and a resistor R101, a common end of the resistor R103 and the resistor R100 is further grounded through a capacitor C95, a common end of the resistor R103 and the resistor R100 is further connected with an anode of a diode D17 through a resistor R104, and a common end of the resistor R100 and the resistor R101 is connected with an anode of the diode D17 through an anode of the diode D91, a forward input end 3 of the operational amplifier U36 is grounded via a capacitor C94, a reverse input end 2 of the operational amplifier U36 is connected to an output end 6 of the operational amplifier U36 via a capacitor C93, a zeroing end 1 of the operational amplifier U36 is connected to a zeroing end 8 of the operational amplifier U37 via a rheostat RPot2, a power supply end 7 of the operational amplifier U36 is connected to VCC12V +, a ground end 4 of the operational amplifier U36 is connected to VCC12V-, the output end 6 of the operational amplifier U36 is connected to a base of the triode Q5 via a resistor R102, the output end 6 of the operational amplifier U36 is connected to a collector of the triode Q5 and a collector of the triode Q6 via a resistor R102, a resistor R99 and a capacitor C89, respectively, an emitter of the triode Q5 is connected to the base of the triode Q6, an emitter of the triode Q6 is grounded via a resistor R106, and a collector of the triode Q5 is grounded via a capacitor C92, the collector electrode of the triode Q5 is connected with the anode of a diode D17 through a capacitor C92 and a rod-shaped resistor R108 in sequence, the cathode of the diode D17 is connected with the 2 end of the interface J5, the 1 end of the interface J5 is connected with the collector electrode of the triode Q5 and the common end of the collector electrode of the triode Q6, a capacitor C90 is connected between the 1 end and the 2 end of the interface J5 in parallel, and the interface J5 is used as the 4-20mA current output interface.

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