CN202720025U

CN202720025U - Electric buoy level gauge based on highway addressable remote transducer (HART) communication

Info

Publication number: CN202720025U
Application number: CN2012202811074U
Authority: CN
Inventors: 王鑫; 杨振荣; 包伟华
Original assignee: Shanghai Automation Instrumentation Co Ltd
Current assignee: Shanghai Automation Instrumentation Co Ltd
Priority date: 2012-06-15
Filing date: 2012-06-15
Publication date: 2013-02-06
Anticipated expiration: 2022-06-15

Abstract

The utility model relates to an electric buoy level gauge based on highway addressable remote transducer (HART) communication; a sampling circuit acquires a level signal and sends the level signal into a multipoint control unit (MCU); the MCU calculates and processes the data, converts the data into analog signals of 4mA to 20mA through a digital-to-analog (D/A) conversion circuit and transmits the signals out; an HART communication interface circuit receives an external level simulation signal, demodulates and converts the signal into a digital signal, and sends the signal to the MCU; the MCU calculates and processes the data, converts the data into analog signals of 4mA to 20mA through the D/A conversion circuit and transmits the signals out; and a power circuit supplies power to all unit circuits. The original cable deployment and control strategies of the electric buoy level gauge can be used continuously; and secondly, extra digital information can be added, so that the installation, the calibration, the maintenance and the control are convenient, a lot of expenses are saved, and meanwhile the measuring precision and the utilization rate of the electric buoy level gauge are improved.

Description

Electric float level meter based on the HART communication

Technical field

The utility model relates to a kind of object position measurement technology, particularly a kind of electric float level meter based on the HART communication.

Background technology

The electricity float level meter is that its sensor is comprised of floating drum (elongated cylindrical) and torsion tube mechanism according to the floating type liquid level instrument of Archimedes principle design.Floating drum is hung vertically on the lever and is immersed in the interior liquid of measuring chamber, and lever and torsion tube mechanism are rigidly connected.When floating drum was in drying regime, the elastic force of torque tube and the self gravitation of floating drum balanced each other, and floating drum is in vacant state.Cause that when liquid level rises buoyancy becomes large, the elastic force of torque tube is corresponding to be reduced, the variation of torque tube angulation, and mandrel and torque tube synchronous rotary are that liquid level changes the angular displacement that converts the torque tube mandrel to and exports with the variation of buoyancy.Corner outputs on the reel cage assembly in the gauge outfit, the magnetic steel component that drive is fixed on the reel cage is subjected to displacement variation, changed the magnetic field that hall effect sensor detects, Hall element is made corresponding Voltage-output, partly converts the current signal output of standard to by electronic circuit.

The electricity float level meter is a kind of of level measurement instrument, is widely used in the industries such as electric power, metallurgy, petrochemical industry, light textile, food, medicine.Along with the application of field bus technique at the industrial process control field, the networking of automated system, total linearize are large trend, original electric float level meter can not carry out digital communication by the control of 4～20mA simulating signal, can not satisfy the requirement of modern industry system.

Because the HART agreement has the characteristics of compatible with digital signal and simulating signal, under the prerequisite that does not affect simulating signal control, can carry out digital communication, have on-the-spot and remote parameter monitoring function, have incomparable advantage aspect reduction system cost, raising control accuracy and the system reliability.

The intelligence instrument that has at present the HART agreement is monopolized by the product of offshore company on the market at home always, because the monopolization of its fancy price and technology, the production cost of domestic enterprise is increased greatly, reduced the competitiveness of enterprise, therefore researched and developed the electric float level meter based on the HART communication with independent intellectual property right and have very large realistic meaning.

Summary of the invention

The utility model be for existing electric float level meter without communication function problem, a kind of electric float level meter based on the HART communication has been proposed, increased digital communication functions on two-wire system electricity float level meter basis, adopt Bell202 fsk signal standard, digital signal and simulating signal are transmitted in non-interfering situation simultaneously, realize both-way communication.

The technical solution of the utility model is: a kind of electric float level meter based on the HART communication, comprise sample circuit, power circuit, HART communication interface circuit, MCU control module and man-machine interface, man-machine interface receives the outer setting instruction, with the communication of MCU control module, sample circuit is sent into the MCU control module after gathering thing position signal, is converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and sends out; After the HART communication interface circuit receives outside thing position simulating signal, demodulation is converted to digital signal and send the MCU control module, be converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and send out, power circuit is the unit circuit supply.

Described HART communication interface circuit comprises MCU interface and transformer coupled interface, and MCU itself can be used as communication interface with HART MODEM with serial ports.The MCU interface is selected the A5191 chip in the described HART communication interface circuit, and the HART agreement adopts the Bell202 frequency shift keying signal of standard to communicate with 1200 baud rates in the A5191 chip.

The beneficial effects of the utility model are: the utility model is based on the electric float level meter of HART communication, and original cable arrangements and control strategy can continue to play a role; Secondly, can increase extra numerical information, be convenient to installation, adjustment, maintenance and control, thereby saved a large amount of expenses, improve again measuring accuracy and the utilization factor of electric float level meter simultaneously.

Description of drawings

Fig. 1 is that the utility model is based on the electric float level meter theory diagram of HART communication;

Fig. 2 is that the utility model is based on HART communication interface figure in the electric float level meter of HART communication.

Embodiment

The utility model electric signal corresponding to thing position signal converts to by sampling unit, by MCU control circuit unit the control of A/D sample circuit is obtained the thing place value, after carrying out data processing and computing, convert corresponding 4～20mA analog output signal to and be sent to the master-control room reception; Simultaneously, the HART communication interface circuit detects the external control signal that is superimposed upon on 4～20mA direct current signal, demodulates the digital signal of stack, sends CPU to and processes; The result who processes is the alternating signal of HART semaphore request and is superimposed upon on the direct current signal through HART communication interface circuit modulation conversion, thus the digital communication of realization and external information.In the utility model, main variable and control information are transmitted by 4～20mA, in the situation that needs, other procedure parameters, device configuration, calibration and configuration info are accessed in the mode of digital communication by the HART agreement.

As shown in Figure 1 based on the electric float level meter theory diagram of HART communication, electric float level meter based on the HART communication is comprised of sample circuit, power circuit, HART communication interface circuit, MCU control module and man-machine interface, man-machine interface receives the outer setting instruction, with the communication of MCU control module, sample circuit is sent into the MCU control module after gathering thing position signal, is converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and sends out; After the HART communication interface circuit receives outside thing position simulating signal, demodulation is converted to digital signal and send the MCU control module, be converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and send out, power circuit is the unit circuit supply.

MCU control module: the inner 12-Bit AD converter of MCU control module, have super low-power consumption and can directly drive LCD, can save many peripheral chips up to the FLASH storer of 60KB and the RAM of 2KB, greatly simplify hardware circuit design.

The HART communication interface circuit: this interface usefulness MCU and HART MODEM chip development are based on the electric float level meter of HART communication, and be simple and convenient, dwindled space and cost.The main functional modules of HART MODEM is comprised of steering logic, carrier detect, modulation and demodulation four parts.The function of it is integrated input filter and output Shaping can be simplified the reliability that interface circuit design realizes system.

The HART communication interface circuit mainly is made of MCU interface and transformer coupled interface.MCU itself can be used as the communication interface of itself and HART MODEM with serial ports.

When occurring the frequency signal of 1200 (± 10) Hz or 2200 (± 20) Hz on the IRXA of the A5191 pin, then the OCD pin of A5191 is high level, MCU sets high level with P1.3 after P1.6 detects high level, this moment, the INRTS pin of HART MODEM detected high level, opens detuner the digital signal that detects is carried out demodulation and send valid data to MCU by ORXD processing.

If OCD is low level, illustrate that bus is idle, at this moment to set P1.3 also be low level to MCU, then the modulator of A5191 is opened, and is sent by the OTXA pin after the Data Modulation shaping that will receive from ITXD.Transformer coupled to 4～20mA direct current signal by operational amplifier amplification and process by the data that OTXA sends.

The HART agreement adopts the Bell202 frequency shift keying signal of standard to communicate with 1200 baud rates.Its Physical layer adopt two kinds of different frequencies (1200Hz and 2200Hz, represent respectively 2 systems 1 and 0) sinusoidal signal, be superimposed upon on 4～20mA signal and communicate because the average of sinusoidal signal is 0, do not disturb direct current signal.It can make simulating signal and digital signal can carry out two-way communication simultaneously and do not interfere with each other.

What the utility model adopted is semiduplex communication, adopts the three layer model structure of simplifying, i.e. ground floor Physical layer, second layer data link layer and layer 7 application layer.Physical layer specifies the transmission method of signal, transmission medium; Data link layer has been stipulated the form of HART frame, and the link communication function realizes setting up, safeguards, terminates; Application layer regulation HART command set.Order is divided three classes, i.e. generic command, normal commands and specific command.Generic command provides all functions relevant with field apparatus, and these orders comprise: read manufacturing firm and device type; Read initializaing variable and unit; The number percent of reading current output and range; Read 4 predefined dynamic variables; Read and write 8 character items, 16 character descriptors, date; Read and write 32 character informations; Read range, unit and damping time constant; Read transducer series number and boundary; The Assembly part numeral of read-write most end; Write polling address.Commonly used command provides the function in the common various field equipment, but is not whole.Comprise and read an altogether group selection of 4 dynamic variables; Write variable damping time; Write range; (zero setting, put maximum range) is measured in calibration; Fixing output current is set; Carry out self check; Carry out host reset; Adjust initial change zero; Write initializaing variable unit; Adjust digital-analog convertor zero point and gain; Write tansfer function; Write transducer series number; Read-write dynamic variable assignment.Specific command only provides for the function of special field apparatus, is that the utility model is controlled oneself peculiar, not compatible.

Because the data transfer rate of HART agreement regulation is 1200bit/s, 10 milliseconds around an of character of every transmission, so adopt the mode transceiving data that interrupts in the software, all the other times can make CPU enter low power consumpting state or process other affairs.The reception of the USART module of MSP430, transmission buffer memory all can produce independently and interrupt, and program is finished the various processing to the HART information frame in this interruption.In the receiving course of frame, unusual whenever detecting, meeting Lookup protocol corresponding state information, program interrupts focusing on mistake, the delay that occurs in the transmission course at timer, and calls corresponding processing procedure according to the difference of system works pattern.The process of transmitting of information frame similarly, when system works during in group schema, the command information whether steady arm constantly has main frame to upload on the detection line at a certain time interval if do not have, can send the form of the relevant information of equipment operation with the HART information frame automatically; If just there is main frame to communicate by letter, then preferentially carries out Host Command, or postpone or cancel the transmission of burst data according to the Host Command type.

Claims

1. electric float level meter based on the HART communication, it is characterized in that, comprise sample circuit, power circuit, HART communication interface circuit, MCU control module and man-machine interface, man-machine interface receives the outer setting instruction, with the communication of MCU control module, sample circuit is sent into the MCU control module after gathering thing position signal, is converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and sends out; After the HART communication interface circuit receives outside thing position simulating signal, demodulation is converted to digital signal and send the MCU control module, be converted to 4～20mA simulating signal by the D/A change-over circuit after the MCU control module computing data and send out, power circuit is the unit circuit supply.

2. described electric float level meter based on the HART communication according to claim 1 is characterized in that, described HART communication interface circuit comprises MCU interface and transformer coupled interface, and MCU itself can be used as communication interface with HART MODEM with serial ports.

3. described electric float level meter based on the HART communication according to claim 2, it is characterized in that, the MCU interface is selected the A5191 chip in the described HART communication interface circuit, and the HART agreement adopts the Bell202 frequency shift keying signal of standard to communicate with 1200 baud rates in the A5191 chip.