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Calibration and comparison of electromagnetic flowmeter

Author: Release date: March 3, 2017 08:57:54 Source: Shanghai Cixi View: 59
In order to determine the flow value of electromagnetic flowmeter or the accuracy of flow measurement value, the electromagnetic flowmeter must be calibrated. Calibration is sometimes called calibration or calibration. In fact, calibration includes two aspects: 1) transfer the measurement value to the instrument to determine the position of the flow scale mark (or determine the output signal of the flow scale); 2) adjust the output of the instrument to compare with the standard value (reference ratio) to judge the accuracy of the instrument and determine its error value.
In the past, the flow meter industry used to calibrate the transmission property of the flow value with the flow "calibration", the hydrology and water industry used to call it "calibration", and the user's calibration process to judge the accuracy of the instrument was called the flow "calibration". Now that the names are more consistent, use "calibration" instead. The national authorized flow laboratory is also named "flow calibration laboratory".
There are two methods for flow calibration of electromagnetic flowmeter: direct measurement method and indirect measurement method.
The direct measurement method, also known as the real flow calibration method, uses the actual fluid to flow through the calibrated instrument, and then uses other standard devices (standard flowmeter or flow standard measuring instrument) to measure the flow rate of the fluid flowing through the instrument, and compares it with the flow value of the calibrated instrument. This method is called wet calibration. The flow value obtained by the real flow calibration method is reliable and accurate, which is used by many flow meters (such as electromagnetic flowmeter, volumetric flowmeter, turbine flowmeter, Coriolis mass flowmeter) and used as a method to establish standard flow rate.
Before the electromagnetic flowmeter leaves the factory, the real flow calibration method is used to complete the flow value transfer process on the flow calibration standard device (sometimes referred to as the flow standard device or flow calibration device). The user unit shall also carry out real flow calibration on the flow calibration standard device after regular verification and maintenance.
The flow calibration standard device is established in accordance with relevant standards and verification regulations, and is recognized by the special organization authorized by the state. It can transfer the flow value. It is the calibration equipment that provides the flow value, and its value can be traced to the national measurement standard of quality, time and temperature.
Dry calibration is an indirect calibration method, which measures the flow area and magnetic flux density B of the electromagnetic flow sensor, calculates the flow value and obtains the corresponding accuracy. Dry calibration is a calibration method to solve the problem that the large diameter electromagnetic flowmeter can not achieve real flow calibration in the 1970s. It has been used as the content of the Japanese Industrial Standard JIS z8764-1975 "method of measuring flow rate by electromagnetic flowmeter". Due to the relatively low accuracy, it has been rarely used. The content of dry calibration in Japanese Industrial Standard JIS Z 8764 "electromagnetic flowmeter" revised in 1986 is no longer the text, but moved to the explanation part (equivalent to the appendix and compilation description of Chinese standard).
On site "flow comparison" refers to the comparison of electromagnetic flowmeter with other "reference flow" on site, such as the measured value of temporarily clamped ultrasonic flow away from the machine, and the measured liquid volume in the inflow pipeline system can be used as the "reference flow". "Flow comparison" is only a kind of auxiliary inspection to evaluate the measured value of electromagnetic flowmeter, the gross error range, and to judge whether the instrument is normal or faulty.

The above is the introduction of Shanghai Cixi on the calibration and comparison of electromagnetic flowmeter, I hope it can help you, if you still have related product problems, you can call the page for consultation! The company provides 24-hour service!

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