CN2529206Y

CN2529206Y - Intelligent electromagnetic flowmeter

Info

Publication number: CN2529206Y
Application number: CN 02208234
Authority: CN
Inventors: 孙向东; 陈助青
Original assignee: Yiwu City Instr Co ltd
Current assignee: Yiwu City Instr Co ltd
Priority date: 2002-03-15
Filing date: 2002-03-15
Publication date: 2003-01-01
Anticipated expiration: 2012-03-15

Abstract

The utility model discloses an electromagnetic flowmeter, which comprises a sensor, an excitation circuit, a microprocessor control circuit and a fan-out circuit; in a singlechip control circuit, a CAN field bus fan-out interface is arranged on the singlechip; one terminal CAN-L of the fan-out bus is connected with a fan-out terminal CRX0 and P1 end P1.6/CTX0; another terminal CAN-H is connected with a fan-out terminal CRX1 and P1 end P1.7/CTX1; in addition, the connection is very convenient; the fan-out control signal in the control terminal of the singlechip is connected to the excitation circuit through a photoelectricity coupling device U9, U10, U11 and U12, and then the fan-out impulse excitation circuit is connected to an excitation wiring. The utility model can solve the anti-jamming problem effectively as well as enhancing the measuring precision and transfer efficiency. The utility model is suitable to a new-generation intelligent electromagnetic flowmeter.

Description

Intelligent electromagnetic flowmeter

Technical field

The utility model belongs to electromagnetic flowmeter.

Background technology

Flow measurement kind various, because of principle different different.The document of electromagnetic flowmeter is also many, has been combined into new technology after the nineties of last century end, and having formed collection sensor technology, microcomputer measurement control and digital communication and transmission is the new feature of one.Chinese patent ZL98225207 discloses a kind of intelligent electromagnetic flowmeter, and with common the same, it includes sensor, field circuit, microcomputer control circuit and output circuit; In the other document also relevant for utilizing fieldbus and HART agreement to realize the communication transmission, and the application that utilizes low frequency square wave excitation mode operation logic.But existingly comprise that intellectual electromagnetic flowmeter exists because of electric network source disturbs to measuring accuracy being difficult to improve two not high problems of communication speed of bringing with the Point-to-Point Data Transmission protocol mode and still exist.

Summary of the invention

The utility model is intended to propose a kind of electromagnetic flowmeter technical scheme that can better address the above problem.Intelligent electromagnetic flowmeter of the present utility model, include sensor, field circuit, microcomputer control circuit and output circuit, it is characterized in that in the said single chip machine controlling circuit, singlechip chip is provided with the fieldbus output interface, and of output bus meets end CAN-L and is connected with P1 mouth P1.6/CTX0 with its output terminal CRX0, and another connects holds CAN-H to be connected with P1 mouth P1.7/CTX1 with its output terminal CRX1; Its single-chip microcomputer U8 control end P0 mouth P0.0/AD0 receives the photoelectrical coupler U12 of field circuit device, the input end of U9, P0 mouth P0.1/AD1 receives the photoelectrical coupler U10 of field circuit device, the input end of U11, and output terminal K1, the K2 of field circuit device are access to field coil.

The utility model has adopted the digit pulse current excitation, and its pulsed frequency can be away from the alternative frequency of electrical network, thereby has reduced interference effectively, makes transducing signal more stable, has improved measuring accuracy.Utilized CAN fieldbus and corresponding host-host protocol work, usability is improved, and can support the serial communication network of distributed real-time control, and its communication speed height reaches as high as 1Mbps, and under 5Kbps speed, maximum total line length can reach 10Km.Its communication speed and transmission range are apparently higher than Hart bus and RS485 bus.

Description of drawings

Fig. 1 is the circuit structure block diagram of intelligent electromagnetic flowmeter.

Fig. 2 is the circuit theory diagrams of intelligent electromagnetic flowmeter.

Wherein: I, input circuit II, filter amplification circuit III, sampling keep and differential amplifier circuit

IV, A/D analog to digital conversion interface circuit V, photoelectricity coupled circuit VI, embedded scm

VII, synchronous electric sampler circuit VIII, digital excitation circuit I X, CAN fieldbus output circuit

Embodiment

Be further described below in conjunction with above-mentioned illustrated embodiment.

This electromagnetic flowmeter is according to the work of faraday electromagnetic induction principle.Conducting liquid produces induction electromotive force by cutting magnetic line when measuring channel flows, and the size of induction electromotive force is directly proportional with its flow velocity, and recording induced potential by the electrode of tube wall cross section upper and lower settings just can be in the hope of flow.Be conductive fluid when flowing through electrode, under the effect of exciting current, from electrode SIG1, SIG2 obtains electromotive force becomes signal of sensor.Its relational expression is:

Q＝π/4(D ²v)＝πDe/4B

Wherein: Q is a flow, and D is the pipeline internal diameter, and B is a magnetic flux density, and v is a mean flow rate,

E is an electromotive force.

Intelligent electromagnetic flowmeter mainly partly is made up of measuring section mechanical part that comprises sensor and testing circuit device, and its structure and work block diagram are as shown in Figure 1.Its measuring tube 1 is the metal tube of nonmagnetic material, is provided with coil, iron core and electrode.Two electrodes 2 produce induced voltage signal under the digit pulse exciting current effect of field coil 3, enter signal preamplifier 4 and carry out the preposition amplification of signal, and after low-pass filter 5 is done the filtering amplification, improve signal to noise ratio (S/N ratio) and semaphore, pass through capacitor-coupled again, eliminate DC component and zero point drift, being input to sample circuit 6 samplings under the control of synchronous electric sampler 11 keeps, do mould/number conversion by A/D converter 7 again, digital signal after the conversion is delivered to MCU single-chip microcomputer 9 and is made the flow calculation process after photoelectrical coupler 8 is isolated, single-chip microcomputer output control signal one tunnel is communicated with synchro switch 11, another road is communicated with digital field circuit device 10, the output of gating pulse exciting current one the tunnel outputs to 12 demonstrations again.The communication output signal then connects output by CAN fieldbus 13, leads to far-end control center.

Fig. 2 has provided the circuit theory diagrams of intelligent electromagnetic flowmeter embodiment.Mainly nine parts being represented by the diagram frame of broken lines are formed, they are: I, input circuit, II, filter amplification circuit, III, sampling keep and differential amplifier circuit IV, A/D analog to digital conversion interface circuit, V, photoelectricity coupled circuit, VI, embedded scm, VII, synchronous electric sampler circuit, VIII, digital excitation circuit, IX, CAN fieldbus output circuit.Input circuit I is made of resistance R 1, R2, R3 and chip U1 (INA118U), resistance R 1, R2 are access to two electrode SIG1, SIG2 of sensor respectively, obtain input signal, through the preposition amplification of chip, enter a back level filter amplification circuit II from the signal of its 6 pin output and carry out low-pass filtering, amplifier chip U2 further amplifies signal.C3 is a coupling capacitance.Back frame III constitutes sampling hold circuit by chip U3A, U3B (CD4066) and resistance R 10, R11, capacitor C 4, C5, and the amplifying circuit that chip U6 (INA118U) constitutes is again with the differential amplification of sampled signal.Chip U7 (MCP3201) among the frame IV is used for the A/D conversion, and this interface circuit carries out the opto-electronic conversion isolation through photoelectricity coupled circuit V and is connected with the embedded scm embedded scm U8 (P87C592EFA) of frame VI.Its input has all been adopted the photoelectricity quarantine measures with being connected of control section.10,9,8,7 pin of U8 connect the operation control knob.

The synchronous electric sampler circuit that the P5 mouth pin 65,66 of embedded scm U8 outputs a control signal to frame VII respectively goes to control U3A, U3B sampling.In addition, the exciting current of numerically controlled field circuit VIII is by Single-chip Controlling, and the CAN fieldbus output circuit output signal of frame IX is also exported by Single-chip Controlling.Its control end P0 mouth P0.0/AD0 receives the input end of the photoelectrical coupler U12 (4N25) of field circuit device, P0 mouth P0.1/AD1 receives the input end of the photoelectrical coupler U10 of field circuit device, by controlling and driving triode VT1, VT2, the base stage of VT3, VT4 produces pulse current, output terminal K1, the K2 of field circuit device are access to field coil, accurately exporting the control excitation frequency by single-chip microcomputer is 6.25HZ, because it comes from single-chip microcomputer rather than takes from the frequency division of electrical network 50HZ, so can not be subjected to the interference of electrical network.

Embedded scm U8 (P87C592EFA) is provided with CAN fieldbus output interface, one of CAN output bus meets end CAN-L and is connected with P1 mouth P1.6/CTX0 pin 23 with U8 output terminal CRX0 pin 57, and another connects holds CAN-H to be connected with P1 mouth P1.7/CTX1 pin 24 with U8 output terminal CRX1 pin 56.Resistance R 15, R17 among the figure, R16, R18 mainly play the impedance matching effect, finish communications smoothly with this and connect, and finish the application layer task of information processing according to the interface case of particular user application program.Practice shows that this field-bus interface extremely is suitable for the application scenario to electromagnetic susceptibility, line failure tolerant and the restricted requirement of anti-transient process.

The P2 mouth pin 40,41,42 of embedded scm U8 corresponds to CS, CLK and the DATA end of display device respectively, uses for showing to connect.

Claims

1, a kind of intelligent electromagnetic flowmeter, include sensor, field circuit, microcomputer control circuit and output circuit, it is characterized in that in the said single-chip microcomputer U8 control circuit, singlechip chip (P87C592EFA) is provided with the fieldbus output interface, and of output bus meets end CAN-L and is connected with P1 mouth P1.6/CTX0 with its output terminal CRX0, and another connects holds CAN-H to be connected with P1 mouth P1.7/CTX1 with its output terminal CRX1; Its single-chip microcomputer U8 control end P0 mouth P0.0/AD0 receives the photoelectrical coupler U12 of field circuit device, the input end of U9, P0 mouth P0.1/AD1 receives the photoelectrical coupler U10 of field circuit device, the input end of U11, and output terminal K1, the K2 of field circuit device are access to field coil.