Calibration and comparison of electromagnetic flowmeters

In order to determine the accuracy of the flow value or flow measurement value of the electromagnetic flowmeter, the electromagnetic flowmeter must be calibrated. Calibration is sometimes also called calibration or verification. In fact, calibration includes two aspects: ①Transfer the value to the meter, determine the position of the flow scale mark (or determine the signal output by the flow scale); ②Adjust the output of the meter and the mark to determine the electromagnetic flowmeter The accuracy of the flow value or the flow measurement value must be calibrated to the electromagnetic flowmeter. Calibration is sometimes also called calibration or verification. In fact, calibration includes two aspects: ①Transfer the value to the meter, determine the position of the flow scale mark (or determine the signal output by the flow scale); ②Adjust the output of the meter to the standard value (reference value). Compare to determine the accuracy of the instrument and determine its error value. In the past, the flow meter industry used to calibrate the nature of flow value transfer with flow 'calibration'. In the hydrology and water industry, it is commonly called 'calibration'. The user's calibration process to determine the accuracy of the meter is called flow 'calibration'. Now these names are gradually becoming the same, use 'calibration' instead. The flow laboratory authorized by the state is also named 'Flow Calibration Laboratory'. There are two methods for the flow calibration of electromagnetic flowmeter: direct measurement method and indirect measurement method. The direct measurement method is also known as the real flow calibration method. It is based on the actual fluid flowing through the meter to be calibrated, and then using other standard devices (standard flowmeter or flow standard measuring instrument) to measure the flow of the fluid flowing through, and the flow rate of the meter being calibrated The flow value is compared, this method is called wet calibration (wet calibration). The flow value obtained by the real flow calibration method is both reliable and accurate. It is used by many current flow meters (such as electromagnetic flow meters, positive displacement flow meters, turbine flow meters, and Coriolis mass flow meters), and is used as a standard flow meter. method. The manufacturer uses the real flow calibration method to complete the flow value transfer process on the flow calibration standard device (sometimes referred to as the flow standard device or the flow calibration device) before the electromagnetic flowmeter leaves the factory. The user must also perform real-flow calibration on the flow calibration standard device for the meter after regular verification and overhaul. The flow calibration standard device is established in accordance with the relevant standards and verification regulations, and is recognized by a special agency authorized by the state. It can be used as a flow rate value transfer device. It is a calibration device that provides a flow rate value. The value can be traced to quality and time. The national benchmark quantity of temperature and temperature. Dry calibration is an indirect calibration method, which measures the structural dimensions such as the flow area of u200bu200bthe electromagnetic flow sensor and the magnetic flux density B, calculates the flow value, and obtains the corresponding accuracy. Dry calibration is a calibration method to solve the problem of real-flow calibration of large-caliber electromagnetic flowmeters in the 1970s. It used to be the content of the Japanese Industrial Standard JIS Z8764-1975 'Method of Measuring Flow Rate Using Electromagnetic Flowmeter'. Due to its relatively low accuracy, it is rarely used now. The content of dry calibration in the Japanese Industrial Standard JIS Z 8764 'Electromagnetic Flowmeter' revised in 1986 is no longer part of the main text, but moved to the explanation part (equivalent to the appendix and compilation instructions of the Chinese standard). On-site 'flow comparison' refers to comparing the electromagnetic flowmeter with other 'reference flow rates' on site. For example, the measured value of the temporarily clamped ultrasonic flow away from the machine, the volume of the liquid that has been measured in the piping system, etc. can be used as 'Reference Flow'. 'Flow rate comparison' is only an auxiliary inspection to evaluate the measured value of the electromagnetic flowmeter, the general error range, and to determine whether the meter is normal or malfunctioning.