Rubber lining for electromagnetic flowmeter

Rubber lining for electromagnetic flowmeter

That is to say, the active buzzer has an internal oscillation source, so it will sound as soon as it is powered on. And there is no oscillation source inside the passive source, so if a DC signal cannot make it sound, it must be driven by a 2K-5K square wave. Active buzzers are often more expensive than passive ones because they have an additional oscillation circuit inside. Starting from the EasyARM-i.MX283 development kit, we will design an active buzzer driven by a 3.3V NPN transistor. We will analyze the problems in the circuit design from actual products and propose improvement solutions for the circuit. This will enable readers to learn how to analyze and improve the circuit from a small buzzer circuit, and design more products, achieving the effect of sparking further discussion.

Electromagnetic flowmeters (EMF) are a new type of flow measurement instrument that rapidly developed in the 1950s and 1960s with the advancement of electronic technology. An electromagnetic flowmeter is an instrument that uses the principle of electromagnetic induction to measure the flow rate of a conductive fluid based on the induced electromotive force when the fluid passes through an external magnetic field.

Rubber lining for electromagnetic flowmeter

The concept of "triggering" can be called the soul level of digital oscilloscopes. Without appropriate triggering conditions, waveform observation cannot be discussed. Although many engineers are familiar with triggering functions, they only know the surface and not the inside. How to gain a deeper understanding of triggering? This ZDS oscilloscope development note is shared with everyone here. When using an oscilloscope, the first step is to obtain a stable triggering waveform in order to ensure the reliability of advanced functions such as measurement and decoding in the future. The triggering function of digital oscilloscopes is becoming increasingly powerful, from conventional triggering, to protocol triggering, and then to template triggering. However, in basic trigger settings, the role of some small details cannot be ignored. After flexible mastery, it is also beneficial for using oscilloscopes.

structure

The structure of an electromagnetic flowmeter mainly consists of a magnetic circuit system, a measuring conduit, electrodes, a housing, a lining, and a converter.

Magnetic circuit system: Its function is to generate a uniform DC or AC magnetic field. The DC magnetic circuit is implemented using magnets, which has the advantages of a relatively simple structure and less interference from AC magnetic fields. However, it can easily polarize the electrolyte liquid inside the measuring tube, causing the positive electrode to be surrounded by negative ions and the negative electrode to be surrounded by positive ions, resulting in electrode polarization and an increase in internal resistance between the two electrodes, which seriously affects the normal operation of the instrument. When the diameter of the pipeline is large, the magnet is also large, bulky, and uneconomical. Therefore, electromagnetic flow meters generally use alternating magnetic fields and are excited by a 50HZ power supply.

1. Measurement is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity;

2. Measure the flow components inside the tube, with no pressure loss and low requirements for straight pipe sections. Adaptability to slurry measurement;

3. Reasonably selecting sensor lining and electrode materials, which have good corrosion resistance and wear resistance;

4. The converter adopts a novel excitation method, with low power consumption, zero point stability, and high degree. The flow range can reach 150:1;

5. The converter can be integrated or separated from the sensor;

6. The converter adopts a 16 bit high-performance microprocessor, 2x16 LCD display, convenient parameter setting, and reliable programming;

7. The flowmeter is a bidirectional measurement system equipped with three integrators: forward total, reverse total, and differential total; It can display positive and negative flow rates and has multiple outputs: current, pulse, digital communication HART；

8. The converter adopts surface mount technology (SMT) and has self checking and self diagnostic functions;

9. The measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity. The sensor's induced voltage signal is linearly related to the average flow rate, resulting in high measurement accuracy.

10. There is no obstruction in the measuring pipeline, so there is no additional pressure loss; There are no movable parts inside the measuring pipeline, so the sensor has an extremely long lifespan.

11. Due to the fact that the induced voltage signal is formed in the entire space filled with a magnetic field and is the average value on the surface of the pipeline, the sensor requires a shorter straight pipe section, with a length of 5 times the diameter of the pipeline.

12. The converter adopts advanced microcontroller (MCU) and surface mount technology (SMT), with reliable performance, high accuracy, low power consumption, stable zero point, and convenient parameter setting. Click on the Chinese display LCD to show cumulative flow, instantaneous flow, flow rate, flow percentage, etc.

13. A bidirectional measurement system that can measure both forward and reverse flow rates. Using special production processes and high-quality materials to ensure the stability of product performance over a long period of time.

For example, the commonly used S8050 has a dissipated power of 0.625W at 25 ℃ (Tc), a rated current of 0.5A, and a node temperature of 150 ℃. The following formula can be used to calculate Rja as 200 ℃/W (Rja represents the thermal resistance from the node to the air). Assuming the chip shell temperature (Tc) is 55 ℃ and the heat dissipation power is 0.5W, the junction temperature of the chip at this moment is: Tj=Tc+PD * Rjc substituted to obtain 155 ℃, which has exceeded the junction temperature by 150 ℃. Therefore, it is necessary to reduce the usage, but the reduction curve is not indicated in the data manual, so the editor can only calculate it on their own.

Instructions for use

The electromagnetic flowmeter has two operating states: automatic measurement state and parameter setting state.
When the instrument is powered on, it automatically enters the measurement state. In automatic measurement mode, the electromagnetic flowmeter automatically completes various measurement functions and displays corresponding measurement data. In the parameter setting state, the user uses four panel keys to complete the instrument parameter setting.
1. Key function

1.1 Key functions in automatic measurement mode
Down key: Loop through the selection screen to display content in the downward direction;
Up key: Loop through the screen to select the up display content;
Composite key+confirm key: enter parameter setting state;
Confirm button: Return to automatic measurement mode;
Adjustment of LCD display contrast in measurement state: The small LCD is adjusted by pressing the "composite key+up key" or "composite key+down key" for a few seconds; The large LCD is achieved by adjusting the potentiometer on the back of the large LCD.
1.2 Key functions in parameter setting state
Down key: Subtract 1 from the number at the cursor;
Up key: add 1 to the number at the cursor;
Composite key+down key: Move the cursor to the left;
Composite key+up key: Move the cursor to the right;
Confirm key: Enter/Exit submenu;
Confirm button: Press continuously for two seconds in any state to return to automatic measurement mode.
Note: When using the "composite key", you should first press the composite key and then simultaneously hold down the "up key" or "down key"
2. In the parameter setting state, if there is no button operation within 3 minutes, the instrument will automatically return to the measurement state.
3. The flow direction for zero point correction can be selected by moving the cursor to the "+" or "-" on the left and using the "up" or "down" keys to switch it to the opposite direction of the actual flow.
4. To select the unit of flow, you can move the cursor to the original displayed flow unit in the "Flow Range Setting" menu, and then use the "Up" or "Down" keys to switch to meet your needs.
2. Parameter setting function key operation
To set or modify the parameters of an electromagnetic flowmeter, it is necessary to transition the flowmeter from the measurement state to the parameter setting state. In the measurement state, press the "composite key+confirm key" to display the state transition password (0000). According to the confidentiality level, modify the password provided by the manufacturer accordingly. After pressing the "composite key+confirm key" again, it will enter the desired parameter setting state.

Installation of Intelligent Electromagnetic Flow Meter Sensor on Process Pipeline

1. The intelligent electromagnetic flowmeter blockage tube must be filled with medium at any time and cannot work normally without filling or emptying the tube. When the medium is not fully filled in the pipe, the method of raising the height of the outlet pipe at the back of the flowmeter can be used to fill the pipe with the medium, avoiding the incomplete pipe and gas from adhering to the electrode.

2. Vacuum inside the pipeline can damage the lining of the flowmeter, so special attention should be paid.
3. The positive direction of flow should be consistent with the positive direction indicated by the arrow on the flowmeter.
4. The intelligent electromagnetic flowmeter can be installed on straight pipelines, as well as on horizontal or inclined pipelines, but it requires that the center line of the two electrodes be in a horizontal state.
5. For liquid and solid two-phase fluids, vertical installation is used to allow the measured medium to flow from top to bottom, which can evenly wear the lining of the flowmeter and extend its service life.
6. Ensure that there is sufficient space near the pipeline flange for the installation and maintenance of the flowmeter.
If there is vibration in the measuring pipeline, there should be fixed supports on both sides of the flowmeter.
8. If the measuring medium is a heavily polluted liquid, a flowmeter body can be installed in the bypass pipeline without interrupting the process operation, which can be emptied and cleared.
9. When installing a flow meter with PTFE lining, the bolts connecting the flange should be tightened evenly, otherwise it is easy to crush the PTFE lining. Use a torque wrench.

OSI stands for Open Systems Interconnection. The Organization for Standardization (ISO) has developed the OSI model, which defines standards for the interconnection of different computers and serves as the fundamental framework for designing and describing computer network communication. The OSI model divides network communication into 7 layers, namely the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. From the perspective of OSI's 7-layer network model, CAN fieldbus only defines the first layer (physical layer, see ISO11898-2 standard) and the second layer (data link layer, see ISO11898-1 standard); In actual design, these two layers are implemented by hardware, and designers do not need to develop related software or firmware for this. As long as they know how to call the relevant interfaces and registers, they can complete the control of CAN.