1. Accuracy level and function
The performance of universal electromagnetic flow meters on the market varies greatly, with some having high accuracy and multiple functions, while others have low accuracy and simple functions. The basic error of high-precision instruments is (± 0.5%~± 1%) R, while the accuracy of low precision instruments is (± 1.5%~± 2.5%) FS, with a price difference of 1-2 times between the two.
The functional differences of electromagnetic flow meters are also significant. The simple one is to measure one-way flow and only output analog signals to drive the rear instrument; Multi functional instruments include bidirectional flow measurement, range switching, upper and lower limit flow alarm, air traffic control and power cut-off alarm, small signal cut-off, flow display and total calculation, automatic verification and fault self diagnosis, communication with the upper computer, and motion configuration. The serial digital communication function of some models of instruments can be equipped with multiple communication interfaces and dedicated chips (ASICs) to connect to HART protocol systems, PROFTBUS, Modbus, CONFIG, FF fieldbus, etc.
2. Flow rate, full flow rate, range, and caliber
The selected instrument diameter on site may not necessarily be the same as the diameter, and should be determined based on the flow rate. The pipeline flow rate for transporting liquids with different viscosities such as water in the process industry is generally an economic flow rate of 1.5-3m/s. The electromagnetic flowmeter is used on such pipelines, and the sensor diameter should be the same as the pipe diameter. When the electromagnetic flowmeter is at full flow rate, the liquid flow velocity can be selected within the range of 1-10m/s, which is relatively wide. The upper limit flow velocity is theoretically unrestricted, but it is generally recommended not to exceed 5m/s unless the lining material can withstand liquid flow erosion. In practical applications, it is rarely exceeded 7m/s, and exceeding 10m/s is even rarer. The lower limit of flow velocity for full flow rate is generally 1m/s, while some models of instruments have a flow rate of 0.5m/s.
3. Liquid conductivity
The premise of using an electromagnetic flowmeter is that the measured liquid must be conductive and cannot be lower than the threshold (i.e. lower limit). Conductivity below the threshold will result in measurement errors and cannot be used. Even if it changes beyond the threshold, it can still be measured with little change in indication error. When used, it also depends on the length of the flow signal line and its distributed capacitance between the sensor and the converter. The manufacturer's instruction manual usually specifies the length of the signal line corresponding to the conductivity. The instrument with non-contact capacitive coupling large-area electrodes can measure liquids with a low conductivity of 5 × 10-8S/cm.
The conductivity of industrial water and its aqueous solutions is greater than 10-4S/cm, while the conductivity of acid, alkali, and salt solutions is between 10-4 and 10-1S/cm. There is no problem with their use, and the conductivity of low distilled water is also between 10-5S/cm. Petroleum products and solvents with low electrical conductivity cannot be used.
The above three points are the considerations for selecting an integrated electromagnetic flowmeter. To understand how much an integrated electromagnetic flowmeter costs, it is necessary to determine the parameter configuration of the integrated electromagnetic flowmeter after understanding the on-site working conditions, in order to have a more accurate selection and quotation. I believe that choosing the right integrated electromagnetic flowmeter is far more important than the price of the integrated electromagnetic flowmeter. For more questions about the price of integrated electromagnetic flow meters, you can consult the selection engineer of Hangzhou Liance.