The choice of electromagnetic flowmeter is mainly the correct choice of the transmitter, and the converter only needs to be matched with it.
Choice of caliber and range
The diameter of the transmitter is usually the same as that of the piping system. If the piping system is to be designed, the diameter can be selected according to the flow range and flow rate. For electromagnetic flowmeters, the flow rate is suitable for 2 - 4m / s. In special cases, such as solid particles in the liquid, in consideration of wear, the optional flow rate is ≤ 3m / s, for easy to manage the fluid. Available flow rate ≥ 2m / s. After the flow rate is determined, the transmitter diameter can be determined according to qv= D2.
The range of the transmitter can be selected according to two principles: one is that the full scale of the meter is greater than the expected maximum flow value; the other is that the normal flow is greater than 50% of the full scale of the meter to ensure a certain measurement accuracy.
Temperature and pressure selection
There are certain restrictions on the fluid pressure and temperature that the electromagnetic flowmeter can measure. When used, the pressure used must be lower than the working pressure specified by the flowmeter. At present, the working pressure specifications of domestically produced electromagnetic flowmeters are:
Less than 50mm caliber, working pressure is 1.6MPa; 900 mm caliber, working pressure is 1 MPa;More than 1000mm caliber, working pressure is 0.6MPa.
If there are special requirements on the pressure resistance of the transmitter, you can negotiate with the manufacturer.
The operating temperature of the electromagnetic flowmeter depends on the lining material used, which is generally 5 - 70 ° C. Such as special treatment, can exceed the above range, such as the wear-resistant corrosion-resistant electromagnetic flowmeter produced by Tianjin Automation Instrument No.3. The transmitter allows the measured medium temperature to be -40 to 130 °C.
Selection of lining material and electrode tree material
The lining material and electrode material of the transmitter must be correctly selected according to the physical and chemical properties of the medium. Otherwise, the instrument will be damaged quickly due to the corrosion of the lining and the electrode, and the corrosive medium will easily cause an accident if it leaks. Therefore, the electrode and the lining material must be carefully selected according to the specific measurement medium in the production process.
1. Measurements are not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity;
2. There is no obstructed flow component in the measuring tube, no pressure loss, and the requirements of the straight pipe section are low. Unique adaptability to slurry measurement;
3. Reasonable selection of sensor lining and electrode materials, that is, good corrosion resistance and wear resistance;
4. The converter adopts novel excitation mode with low power consumption, stable zero point and high precision. The flow range can reach 150:1;
5. The converter can be integrated with the sensor or separated;
6. The converter adopts 16-bit high-performance microprocessor, 2x16LCD display, convenient parameter setting and reliable programming;
7. The flowmeter is a two-way measuring system with three totalizers: positive total, reverse total and total difference; can display positive and negative flow, and has multiple outputs: current, pulse, digital communication , HART;
8, the converter uses surface mount technology (SMT), with self-test and self-diagnosis function;
9. Measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity. The sensor induced voltage signal has a linear relationship with the average flow velocity, so the measurement accuracy is high.
10. There is no obstruction in the measuring pipe, so there is no additional pressure loss; there is no moving parts in the measuring pipe, so the life of the sensor is extremely long.
11. Since the induced voltage signal is formed in the entire space filled with the magnetic field and is the average value on the pipeline surface, the sensor requires a short straight pipe section and a pipe diameter of 5 times.
12. The converter adopts the latest and most advanced single-chip microcomputer (MCU) and surface mount technology (SMT) in the world. It has reliable performance, high precision, low power consumption, stable zero point and convenient parameter setting. Click on the Chinese display LCD to display the cumulative flow, instantaneous flow rate, flow rate, flow percentage, and more.
13, two-way measurement system, can measure forward flow, reverse flow. Special production technology and high-quality materials ensure that the performance of the product remains stable for a long time.
Application of electromagnetic flowmeter
Because electromagnetic flowmeter has its unique advantages, it is widely used in chemical, chemical fiber, food, paper, sugar, water supply and drainage, environmental protection, water conservancy, steel, petroleum, pharmaceutical and other industrial fields. Various acid and alkali salt solutions, mud, pulp, pulp, coal water slurry, corn syrup, fiber pulp, lime slurry, water supply and drainage, brine, hydrogen peroxide, beer, wort, various beverages, black liquor, green liquor, etc. The volumetric flow of the medium.
The main technical parameters
Nominal diameter series DN (mm)
Pipeline PTFE lining:
10,15,20,25,32,40,50,65,80,100,
125,150,200,250,300,350,400,
450,500,600
Pipeline rubber lining:
40,50,65,80,100,125,150,200,250,
300,350,400,500,600,800,1000,
1200
Special specifications can be customized
Flow direction: current output
Positive, negative, net flow
Range ratio: 150:1
Repeatability error: ±0.1 of the measured value
Accuracy level: pipeline type: 0.5 level, 1.0 level
Measured medium temperature
Ordinary rubber lining: -20 ~ +60 ° C
High temperature rubber lining: -20 ~ +90 ° C
PTFE lining: -30 ~ +100 ° C
High temperature PTFE lining: -30 ~ +180 ° C
Rated operating voltage
Pipe type: DN6-DN100≤1.6Mpa, DN125-DN225≤1.0Mpa high pressure can be customized
Conductivity range:
Conductivity of the measured fluid ≥ 5us / cm (integrated)
Most water-based media have a conductivity of 200-800 us/cm, and electromagnetic flow meters can be used to measure the flow rate.
Load resistance: 0 ~ 10mA, 0 ~ 1.5kΩ
4 to 20 mA, 0 to 750 Ω
Digital frequency output
The upper limit of the output frequency can be set to open the bidirectional output of the open collector of the transistor with optical isolation from 1 to 5000HZ. External ≤35V, the maximum current of the collector is 25mA when conducting
Power supply
85～265V, 45～63HZ
Straight pipe length
Pipeline type: upstream ≥5DN, downstream ≥2DN
Connection method
The flowmeter and the pipe are flanged, and the flange connection size should meet the requirements of GB11988.
Explosion-proof mark: mdllBT4
Ambient temperature: -10 ° C ~ +55 ° C
Relative temperature: 5% to 90%
Total power consumption: less than 15W