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Hi, I’m the Industrial Control Assistant. Briefly. In standard pipeline fluid measurement, flow meters can only measure fluid flowing in one direction; if the direction of the fluid changes, measurement becomes impossible. Flowmeters that can measure the total flow in both directions are rare; the ones we are familiar with under normal circumstances are electromagnetic flowmeters and ultrasonic flowmeters. With electromagnetic flowmeters, the flow direction, whether forward or backward, can be adjusted according to settings. When installed horizontally, selecting the total flow rate provides considerable convenience on site. However, when installed vertically, the liquid flows only from bottom to top according to the flow meter. Electromagnetic flowmeters have strict requirements regarding a full pipe condition; when the liquid flowing through the flowmeter does not meet this requirement, an empty pipe alarm is triggered, and the gauge displays no total flow rate. In the course of use, electromagnetic flowmeters often encounter an empty tube alarm. This alarm indicates whether the measuring tube is filled with liquid or not. To determine the cause of this alarm, one can short-circuit the signal input terminal of the converter to ground; if the measurement shows that the tube goes from empty to full, it means that the converter of the electromagnetic flowmeter is functioning properly. In such cases, the possible causes of the problem are either a low electrical conductivity of the liquid being measured or an incorrect setting for the empty tube threshold. In addition, if there is a problem with the electrodes of the electromagnetic flowmeter, an empty tube alarm will also be triggered. Air traffic control alarm thresholds are often used in conjunction with air traffic control alarm applications. The alarm threshold for empty tubes is generally set at 500%. The empty-tube alarm is a relative value that is often directly related to the tube being full and to the conductivity of the medium. The value of this alarm threshold determines the sensitivity of the empty-tube alarm. Before determining this threshold, it is necessary to first measure the conductivity of the medium in question, as well as its resistance value when the tube is full. Then, by considering factors such as the time it takes for the liquid to adhere to the walls, an appropriate alarm response time can be set; therefore, the threshold for air traffic control alarms should be an adjustable parameter. In practical applications, the resistance value of the resistor when the tube is filled with liquid is defined as 100%; that is, when the tube is full of liquid, the reading for an empty tube is calibrated to 100% using the \"empty tube alarm threshold\". When the liquid level in the pipeline is below the measuring electrode, the relative resistance will increase; when it exceeds the empty tube alarm threshold, the dashboard will display an empty tube alarm. Theoretically, if the air traffic control alarm threshold is set at 900%, an air traffic control alarm will be displayed when air traffic control is active. The lower the air traffic control alarm threshold, the more sensitive the air traffic control alarm is. Each is set according to on-site requirements. Procedure for dealing with an empty tube alarm in an electromagnetic flowmeter: 1. Check whether the liquid fills the measuring tube ； 2. Use a wire to short-circuit the converter’s signal terminals SIG1, SIG2, and SIGGDN3. If the “empty tube” indication is removed at this point, it indicates that under normal conditions the converter is functioning properly; the low conductivity of the liquid being tested is likely the cause, or there may be errors in the settings for the empty tube threshold and range ； 3. Check whether the signal cable is connected correctly ； 4. Check whether the controller electrodes are in normal condition ； 5. Set the total current to zero and check that the conductivity ratio should be less than 100%; 6. When current is present, the resistance values of terminals SIG1, SIG2, and SIGGDN should each be less than 50kΩ. Continuous updates – feel free to follow. We omitted 300 words.