Electromagnetic flowmeter with HART (Highway Addressable Remote Transducer) communication

Abstract

The electromagnetic flowmeter with the HART communication function comprises a 4-20 mA circuit, a Hart communication circuit, a flow processing circuit, a touch key circuit, a display circuit and a microcontroller circuit, FSK signals of HART are transmitted to the 4-20 mA circuit in a carrier mode, and therefore a multi-master-slave communication mechanism or a one-master-multi-slave communication mechanism is achieved. By means of the two 4-20 mA signal lines, current output is achieved, current flowmeter information such as coefficients, instantaneous flow, accumulated flow and alarm information can be output, and stability, long-distance transmission and anti-interference performance are achieved when the current flowmeter is carried on 4-20 mA current signals. Meanwhile, the electromagnetic flowmeter with HART communication can not be externally connected with a power supply any more, and can be directly powered by a 4-20mA signal line, so that the external tedious wiring of the electromagnetic flowmeter is reduced, and the cost is reduced due to the reduction of the power supply line and the external power supply.

Description

Technical Field

[0001] The utility model relates to the field of HART communication, and particularly to an electromagnetic flowmeter with HART communication. Background Art

[0002] Electromagnetic flowmeters are usually applied to industrial sites, where electromagnetic interference, static interference, pulse interference, etc. often occur. Traditional communication methods often experience data disorder and high error rates when dealing with these interferences, affecting the use of on-site equipment. Moreover, the power lines outside the site also have a certain impact on the signal lines. And there are situations where two hosts access the electromagnetic flowmeter simultaneously at some sites. The solution of the utility model not only reduces the number of external wiring, combines the communication line and the power line, reduces the external wiring, but also uses the current output as a medium to reduce the risk of external interference. And the data communication has good anti-interference performance and stability, and can be transmitted over a long distance at the same time. HART communication can also support two hosts to read the electromagnetic flowmeter simultaneously, making the communication more flexible. Summary of the Invention

[0003] The utility model provides an electromagnetic flowmeter with HART communication, which carriers the FSK signal of HART onto the 4-20mA circuit, thereby realizing a multi-master-slave or one-master-multi-slave communication mechanism. An electromagnetic flowmeter with HART communication, through two 4-20mA signal lines, not only realizes the current output, but also can output the current flowmeter information, such as coefficients, instantaneous flow rate, cumulative flow rate, alarm and other information, and has the performance of stability, long-distance transmission and anti-interference when carried on the 4-20mA current signal; at the same time, the electromagnetic flowmeter with HART communication can no longer be externally powered, and directly uses the 4-20mA signal line for power supply, reducing the cumbersome external wiring of the electromagnetic flowmeter. At the same time, due to the reduction of the power supply line and the external power supply, the cost is reduced.

[0004] In order to achieve the above object, the technical solution of the utility model is as follows:

[0005] An electromagnetic flowmeter with HART communication includes a 4-20mA circuit, a HART communication circuit, a flow processing circuit, a key circuit, a display circuit, and a microcontroller circuit, and is characterized in that:

[0006] The 4-20mA circuit converts the flow rate or flow velocity into a current signal through a current loop chip;

[0007] The HART communication circuit can realize data interaction between external devices and the electromagnetic flowmeter;

[0008] The flow processing circuit converts the flow velocity signal into a digital signal;

[0009] The described key circuit is used for users to perform customized function settings through keys;

[0010] The described display circuit can display the parameters of the flowmeter to the user;

[0011] After receiving and verifying and parsing the data, the microcontroller circuit sends the internal flow - related data of the flowmeter to the HART communication circuit through the TTL communication method.

[0012] Advantages of the present utility model:

[0013] (1) The electromagnetic flowmeter with HART communication of the present utility model can achieve current output, power supply and data communication all using the same set of wires. These three functions can be realized with only two wires, reducing wiring and external devices and lowering costs.

[0014] (2) The electromagnetic flowmeter with HART communication of the present utility model loads the flow data onto the 4 - 20mA current output line. This method has strong anti - interference ability, increases the stability of communication, and can support long - distance data transmission due to being a current signal.

[0015] (3) The electromagnetic flowmeter with HART communication of the present utility model contains both analog signals and digital signals, can directly be compatible with traditional analog instrument schemes, and is more flexible in on - site use. Description of the Drawings

[0016] Attached Figure 1 is the principle block diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0017] Attached Figure 2 is the 4 - 20mA circuit diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0018] Attached Figure 3 is the HART communication circuit diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0019] Attached Figure 4 is the key circuit diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0020] Attached Figure 5 is the display circuit diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0021] Attached Figure 6 is the microprocessor circuit diagram of the electromagnetic flowmeter with HART communication of the present utility model.

[0022] Attached Figure 7This is a flow processing circuit of an electromagnetic flowmeter with HART communication for the present utility model. Detailed implementation mode

[0023] The technical solution of the present utility model will be further described in detail below in combination with the detailed implementation mode and the accompanying drawings.

[0024] As Figure 1 shown, an electromagnetic flowmeter with HART communication includes a 4-20mA circuit, a HART communication circuit, a flow processing circuit, a key circuit, a display circuit, and a microcontroller circuit.

[0025] As Figure 2 and in combination with the attached Figure 3 shown: Figure 2 is a 4-20mA current loop circuit that converts the flow rate or velocity into a current signal through a current loop chip. The formula is as follows. Let the current value be I, the flow rate range of the flowmeter be F, and the current flow rate value be V. Then, V = (F / 16)*I – (1 / 4)*F. External devices can detect the current value of the electromagnetic flowmeter in real time and thus know the real-time flow rate value. Moreover, the electromagnetic flowmeter can be powered through two 4-20mA signal lines, reducing external devices and lowering costs. Specifically, the 16th pin of U4 is connected to the 3rd pin of Q1. Q1 is an N-type MOS transistor. The U4 chip drives the output terminal through the internal voltage regulator at the 13th pin. This signal is responsible for driving the external adjustment transistor to establish the corresponding VCC voltage, enabling the U4 chip to also supply power as a power chip. The LOOP+ signal serves as the external power input for the interface when it is a passive 4-20mA. The 5th, 6th, and 7th pins of U4 are the 4-20mA control signal inputs used to adjust different current outputs. The 8th pin of U4 is the current output pin of the chip. When it is an active 4-20mA, the current flows out from the IO port and the power negative flows in. The 10th pin of U4 is the analog filter of the internal switching current source and is connected to the HART chip U5 through C8. U7 is a microcontroller. U7 sends the data to be sent to the U5 chip through the serial port. The U5 chip modulates the data into a HART carrier signal and then, through the 7th pin of U5, couples the HART carrier signal through the C8 capacitor and sends it to U4. Finally, it is sent to the external HART device through the 4-20mA line, realizing the transmission from the controller to the external device. The 14th pin of U5 is the HART signal receiving pin. After the external LOOP+ signal is connected, the HART carrier signal is received by the 14th pin of U5 and converted into a serial port signal and sent to U7, realizing the two-way communication between the external HART device and the flowmeter. At the same time, HART communication can also achieve a multi-master and one-slave communication mode.

[0026] As shown in the attached Figure 4 and the attached Figure 5 shown: As shown in the attached Figure 4It is a key circuit, attached Figure 5 It is a display circuit. U6 is a touch chip that can externally connect 4 touch keys at the same time. P4 is a liquid crystal display interface. Through the touch keys and liquid crystal display, the user can realize the interaction between the electromagnetic flowmeter and the external HART device, and change and set the corresponding parameters.

[0027] As attached Figure 7 As shown: The flow processing circuit of the electromagnetic flowmeter converts the flow velocity signal into a digital signal. Specifically, the flow processing circuit collects and converts the flow signal, and finally U7 analyzes and processes the flow signal, displays the flow data through the liquid crystal display, and sends the flow data to the external device through HART communication.

Claims

1. An electromagnetic flowmeter with HART communication, comprising a 4-20 mA circuit, a HART communication circuit, a flow processing circuit, a key circuit, a display circuit, and a microcontroller circuit, characterized in that: The 4-20 mA circuit converts the flow rate or velocity into an electrical signal through a current loop chip; The HART communication circuit can realize data interaction between external devices and the electromagnetic flowmeter; The flow processing circuit converts the velocity signal into a digital signal; The key circuit is used for users to perform customized function settings through keys; The display circuit can display the parameters of the flowmeter to the user; After receiving and parsing the data, the microcontroller circuit sends the internal flow-related data of the flowmeter to the HART communication circuit through the TTL communication method.

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