Electromagnetic flowmeter

Electromagnetic flowmeter

The voltage value read on the instrument is converted to the current value in the wire through transmission impedance conversion. Transmission impedance is defined as the ratio of the induced voltage on the input impedance of an instrument to the current in the wire. For a specific probe, its transfer impedance ZT can be found in the probe manual provided by the manufacturer. The current in the wire is equal to: I=V/ZT. If all physical quantities in the formula are expressed in dB, they can be directly subtracted. For leaks in the chassis, a near-field probe should be used for detection. The near-field probe can be seen as a very small circular antenna. Due to its small size, it has low sensitivity and can only detect near-field radiation sources. This is beneficial for locating the radiation source.

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.

Electromagnetic flowmeter

Today, we will introduce a national invention authorization - a compensation calibration method and device for RTC module applied in electric energy meters. It should be applied for by State Grid Corporation of China and authorized on August 31, 2018. The present invention relates to the field of power instrumentation technology, particularly to a compensation calibration method and device for RTC (Real Time Clock) module applied in an electric energy meter. For most systems with high time requirements, the RTC modular real-time clock generation module can provide real-time clock for the chip. RTC modules usually have external crystals that output clock signals based on the natural oscillation frequency of the crystal. Their structure is relatively simple and their cost is low.

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.

The following will explain using storage as an index. PrintScreen (one click storage) is a one click storage function belonging to the oscilloscope, which has 7 types of one click shortcut operations. The blue operation keys are easy to recognize and operate. With just one click, the content displayed on the current screen can be saved in the format of "*. png" image. The saving path can be set and saved to local flash memory or external storage USB drive. The content stored with one click will be automatically named and saved in the save path, usually starting with 'dso'. Engineers can simultaneously save multiple files to a USB drive and then view and analyze them on a PC.

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.

The accelerometer responds to static and dynamic acceleration in each axis. 'Static acceleration' may seem like an unfamiliar term, but it involves an important sensor behavior: response to gravity. Assuming there is no dynamic acceleration and sensor errors are eliminated through calibration, each accelerometer output will represent its axis orientation relative to gravity. To determine the actual average orientation that typically occurs in stable systems in the presence of vibration and rapid acceleration, filters and fusion programs (combining readings from multiple sensor types to obtain estimates) are typically applied to the raw measurements. Another type of sensor is a gyroscope, which provides angular velocity measurements.