Thread Content
Yokogawa electromagnetic flowmeters are highly favored by companies in industries such as petrochemicals and chemicals due to their advantages of no pressure loss, high precision, and reasonable price, playing an important role in flow measurement. However, in practical applications, due to improper operation, unsuitable selection of equipment, and unscientific installation, measurement errors are difficult to avoid, causing trouble for users. Therefore, those working in the field of instruments should pay attention to various factors that cause errors in Yokogawa electromagnetic flowmeters. Generally speaking, the main factors causing errors in Yokogawa electromagnetic flowmeters can be divided into three categories: improper selection, the influence of the liquid being measured, and interference. I. Flow velocity of the liquid to be measured: The flow velocity range that can be measured by the Yokogawa electromagnetic flowmeter is generally 0.5–10 m/s, with the optimal flow velocity range being 1.5–3 m/s. In actual use, the inner diameter of the measurement tube should be determined based on the flow rate to be measured and the flow velocity range that the Yokogawa electromagnetic flowmeter can measure. II. Selection of electrode and lining materials: The electrode and lining materials come into direct contact with the liquid to be tested. These materials should be selected based on the properties of the liquid (such as corrosivity and abrasiveness) as well as the operating temperature. If the wrong materials are chosen, issues such as rapid adhesion, corrosion, scaling, wear, and deformation of the lining may occur, leading to measurement errors. III. Excitation Stability: The excitation methods for Yokogawa electromagnetic flowmeters include direct current excitation, alternating current sine wave excitation, and dual-frequency rectangular wave excitation. Direct current excitation can lead to electrode polarization and DC interference issues, while alternating current sine wave excitation may cause fluctuations in the zero point. Dual-frequency rectangular wave excitation combines the excellent zero-point stability of low-frequency rectangular wave excitation with the strong ability to suppress fluid-induced noise from high-frequency rectangular wave excitation, making it an ideal excitation method. In practical applications, it is necessary to ensure stability in power supply voltage and frequency as much as possible, in order to maintain a constant magnetic field strength and reduce measurement errors caused by changes in magnetic field strength. IV. Measurement of fluid mixtures: When using Yokogawa electromagnetic flowmeters to measure the flow rate of liquid-solid mixed fluids (such as water containing sediment), if a Yokogawa electromagnetic flowmeter calibrated for single-phase liquids is used, measurement errors will occur. In such cases, it is necessary to install the sensor in a straight pipe section where no separation between the liquid and solid phases takes place.