From the above analysis, it can be concluded that the false alarms presented by electromagnetic flow meters in measuring cooling water in the steel industry are mostly caused by bubbles rubbing against the electrodes. So, first of all, satisfy the requirement for the length of the upstream straight pipe section on the appearance of the device, standardize the appearance of the device, select a device location far away from the heat source, use pipeline flow rate reasonably, and choose PFA fluoroplastic fabric with high smoothness and high-purity alumina industrial ceramic conduit. These methods will help prevent or reduce the occurrence of vortices and gas separation. That is to say, improving sensor manufacturing technology, enhancing the external environmental and device conditions, and selecting upstream exhaust valves on the surface may prevent the occurrence of doubts. Secondly, setting the external damping time and function reasonably can also handle false alarms caused by measuring bubble noise. The selection of damping time is based on the pulse width of bubble noise in the flow signal. Usually, the damping time should be 3 to 5 times the width of the bubble noise pulse. If the pulse width of bubble noise is 10 seconds, the damping time should be taken as 30-50 seconds. The detailed selection should be based on the requested control accuracy. The control error of 3 times the pulse width is 5%, and the control accuracy of 5 times the pulse width is higher than 1%.

Increasing the external damping time can effectively deal with the impact of pulse type bubble noise, but it also brings the drawback of slow response, that is, when the actual flow rate shakes, the external response is very slow. This is undoubtedly a challenge for the cooling water system that requires active control. To address this issue, intelligent electromagnetic flow meters can use software logic to discriminate and handle gross errors [5]. When presenting this problem, two conditions are used to determine whether it is a change in flow rate or a bubble rubbing against the electrode, namely adjusting the inactive time of the flow rate and changing the fluctuation constraint. If it weren't for the noise caused by bubbles rubbing against the electrodes, the CPU would perform normal sampling, computation, and digital filtering; If it is determined that the occurrence is bubble noise, cut off the measurement value and stick to the previous flow measurement value. So, during normal flow measurement, the damping time is still 3-6 seconds. As long as there is bubble noise, the inactive time will be extended according to the pulse width setting, and the system control time will also be extended.

When we reasonably select the "change rate constraint value" and "inactive time value" of the electromagnetic flow converter with coarse error suppression function, the converter can not only suppress false alarms caused by bubble noise, but also maintain the set damping time value of the external response speed during normal operation.