DN15 electromagnetic flowmeter is mainly used to measure the volume flow of conductive sewage fluid. It can be installed in various sewage discharge sites such as chemical, papermaking, food, textile, metallurgy, environmental protection, water supply and drainage.
DN15 electromagnetic flowmeter performance characteristics:
1. The instrument structure is simple and reliable, without moving parts, and has a long service life.
2. There are no intercepting and obstructing parts, and there is no pressure loss and fluid blockage.
3. There is no mechanical inertia, fast response, good stability, and can be used in automatic detection, adjustment and program control systems.
4. The measurement accuracy is not affected by the type of measured medium and its physical quantity parameters such as temperature, viscosity, density, pressure, etc.
5. The use of polytetrafluoroethylene or rubber lining and different combinations of electrode materials such as Hc, Hb, 316L, Ti, etc. can meet the needs of different media.
6. There are various flowmeter models such as pipeline type and insertion type.
7. Using EEPROM memory, the storage and protection of measurement and calculation data are safe and reliable.
8. It has two types: integrated and separated.
9. High-definition LCD backlight display.
Technical parameters of electromagnetic flowmeter:
1. Instrument accuracy: pipeline type 0.5 level, 1.0 level; insertion type 2.5 level
2. Measuring medium: various liquids and liquid-solid two-phase fluids with conductivity greater than 5μS/cm.
3. Flow rate range: 0.2～8m/s
4. Working pressure: 1.6MPa
5. Ambient temperature: -40℃～+50℃
6. Medium temperature: PTFE lining ≤180℃; Rubber lining ≤65℃
7. Explosion-proof mark: ExmibdⅡBT4
8. Explosion-proof certificate number: GYB01349
9. External magnetic interference: ≤400A/m
10. Housing protection: Integrated type: IP65;
Separate type: Sensor IP68 (5 meters underwater, * for rubber lining); Converter IP65
11. Output signal: 4～20mA.DC, load resistance 0～750Ω
12. Communication output: RS485 or CAN bus
13. Electrical connection: M20×1.5 internal thread, φ10 cable hole
14. Power supply voltage: 90～220V.AC, 24±10%V.DC
15. Power consumption: ≤10VA
 

Classification by excitation method:
To generate a uniform and constant magnetic field, it is necessary to select a suitable excitation method. For example, according to the excitation current method, there are DC excitation, AC (power frequency or other frequency) excitation, low-frequency rectangular wave excitation and dual-frequency rectangular wave excitation.
1. DC excitation:
DC excitation uses direct current or magnets to generate a constant uniform magnetic field. The advantage of this DC excitation transmitter is that it is little affected by the interference of the AC electromagnetic field, so the influence of the self-inductance phenomenon in the liquid can be ignored. However, the use of a DC magnetic field can easily polarize the electrolyte liquid passing through the measuring pipe, that is, the electrolyte is electrolyzed in the electric field to produce positive and negative ions. Under the action of the electric field force, the negative ions run to the positive electrode and the positive ions run to the negative electrode, which will cause the positive and negative electrodes to be surrounded by ions of opposite polarity, seriously affecting the normal operation of the instrument. Therefore, DC excitation is generally only used to measure non-electrolyte liquids, such as liquid metal flow (mercury at room temperature and liquid steel, lithium, potassium at high temperature), etc.
2. AC excitation:
Most electromagnetic flowmeters used in industry use AC excitation of industrial frequency (50Hz) power supply to generate alternating magnetic field, avoiding polarization interference on the surface of DC excitation electrode. However, using AC excitation will bring a series of electromagnetic interference problems (such as orthogonal interference, in-phase interference, zero drift, etc.). Now AC excitation is being replaced by low-frequency square wave excitation.
3. Low-frequency square wave excitation:
There are two types of low-frequency square wave excitation waveforms: binary (positive-negative) and ternary (positive-zero-negative-zero), and its frequency is usually 1/2~1/32 of the industrial frequency. Low-frequency square wave excitation can avoid orthogonal electromagnetic interference of AC magnetic field, eliminate industrial frequency interference caused by distributed capacitance, suppress eddy current caused by AC magnetic field in pipe wall and fluid, and eliminate polarization phenomenon of DC excitation.
 

Measuring performance requirements of electromagnetic flowmeter:
1. Accuracy level:
The accuracy level and allowable error of flowmeter within the specified flow range shall comply with the provisions of Table 1. The relative indication error is used to indicate the flowmeter error.
2. Reference error:
Reference error can also be used to indicate the error of flowmeters used for instantaneous flow indication. The allowable error series should comply with the provisions of Table 1. The accuracy grade will no longer be given in the bid for the calibration results, but the allowable error will be used, and FS should be marked after the allowable error, such as ±0.5%FS.
3. Error expression method and selection principle:
In a calibration of a flowmeter, the flowmeter error expression method should be given according to one of the accuracy grades and reference error; for flowmeters that use a combination of relative indication error and reference error to indicate the error, a unified method should also be used to indicate the error in a calibration. 4. Repeatability:
The repeatability of the flowmeter shall not exceed 1/3 of the allowable error value specified for the corresponding accuracy grade.
 

Technical data of the whole machine and sensor:

Lining options:

Selection of inlet protection flange and grounding flange (or grounding ring):

Electrode selection

Flow range comparison table:

Precautions for installing electromagnetic flowmeter:
1. The installation dimensions must be calculated accurately, otherwise it is easy to leak or fail to install.
2. The flow direction of the fluid must be consistent with the flow direction arrow on the sensor surface.
3. The electrode axis of the flowmeter must be approximately horizontal, otherwise it will affect the measurement accuracy.
4. The flanges on both sides of the sensor must be kept parallel, otherwise it is easy to leak.
5. In order to avoid the formation of vortex flow after installation, it should be ensured that the process piping, seals, and flowmeter coaxial connections cannot be staggered.
6. When installing the flowmeter, it is strictly forbidden to weld close to the flowmeter flange to avoid burning the flowmeter lining.
7. For process pipelines of different properties, the corresponding grounding method should be adopted (see sensor grounding).
8. For corrosive media, it should be installed vertically, and the measured medium flows from bottom to top, so as to avoid the deposition of solid particles in the flowmeter pipeline, make the lining corrode evenly, and extend the service life.
9. For measuring pipes with a diameter greater than 200mm, a telescopic head can be used for convenience.
 

Confirmation of measuring range:
The flow rate of the medium measured by the general industrial electromagnetic flowmeter is preferably 2 to 4 m/s. In special cases, the low flow rate should not be less than 0.2 m/s and should not be greater than 8 m/s. If the medium contains solid particles, the common flow rate should be less than 3 m/s to prevent excessive friction between the lining and the electrode; for viscous fluids, the flow rate can be selected to be greater than 2 m/s. A larger flow rate helps to automatically eliminate the effect of viscous substances attached to the electrode, which is conducive to improving the measurement accuracy.
Under the condition that the measuring range Q has been determined, the size of the flowmeter caliber D can be determined according to the range of the above flow rate V, and its value is calculated by the following formula:
Q=πD2V/4
Q: flow rate (㎡/h) D: pipe inner diameter V: flow rate (m/h)
The measuring range Q of the electromagnetic flowmeter should be greater than the expected flow value, and the normal flow value should be slightly greater than 50% of the full scale of the flowmeter. 
Correct selection:
The selection of electromagnetic flowmeter is a very important task in instrument application. According to relevant data, 2/3 of the failures of the instrument in actual application are caused by incorrect selection and incorrect installation of the instrument, so special attention should be paid.