Alarm phenomena of electromagnetic flowmeters and solutions

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When users use electromagnetic flowmeters, alarms occasionally occur, and it is only natural for them to wonder whether there is a fault somewhere in the flowmeter In fact, specific issues need to be analyzed on a case-by-case basis. The alarm phenomena associated with electromagnetic flowmeters often stem from the following three misconceptions: Misconception 1: Is it true that an excitation alarm or a system alarm in an electromagnetic flowmeter indicates that the flowmeter is damaged? System alarm: SYS – System excitation alarm. In fact, the excitation alarm is the same as the system alarm; it is sometimes also referred to as system excitation alarm. It represents an alarm related to the excitation signal detected by the intelligent electromagnetic flowmeter. When customers encounter this issue, it is usually due to excessive pipe vibration, or moisture entering the wiring box during use, which results in an open circuit in the excitation coil. Solutions for alarms in electromagnetic flowmeter systems: The solution is quite simple; users can use a multimeter to check whether the excitation circuit is intact or not. The relevant terminals are EXT+ and EXT–; by measuring the resistance at these terminals, it is possible to determine the cause of any interruption in the excitation circuit. Specific judgment criterion: The resistance value of the excitation coil shall not exceed 200Ω. There is another case involving battery-powered electromagnetic flowmeters, where the excitation alarm is triggered by detecting the resistance value of the excitation coil. Although this alarm occurs, it does not affect the measurement results, and users can resolve this issue by adjusting the excitation method. Myth 2: Is an empty tube alarm in an electromagnetic flowmeter an indication of a fault with the instrument? Flow control alarm: FGP – Fluid flow control alarm. Intelligent electromagnetic flowmeters generally have flow control detection functionality and do not require additional electrodes. When the user selects the empty pipe alarm, and the fluid level in the pipe is below the measuring electrode, the intelligent electromagnetic flowmeter can detect an empty pipe condition. When this condition is detected, both the analog and digital output signals of the instrument are 0, and the flow display on the instrument is also 0. The purpose of the empty pipe alarm in electromagnetic flowmeters is to enable customers to know in real time the flow condition of the medium within the measurement pipeline, as well as whether the pipe is empty or full. This is particularly useful for those sections of pipes that are not transparent, as it provides users with a convenient and fast way to determine the fluid status inside the pipe, reflecting the user-friendly and intelligent design of these flowmeters. Therefore, the empty pipe alarm in an electromagnetic flowmeter does not indicate a malfunction of the flowmeter; rather, it reflects the actual condition of the fluid within the measurement pipeline. Of course, users can choose to disable this setting as needed. Myth 3: Do the upper flow limit alarm and lower flow limit alarm of an electromagnetic flowmeter indicate that it has exceeded its range? FQH – Alarm for upper flow limit; FQL – Alarm for lower flow limit. The alarms for the upper and lower flow limits are calculated as percentages of the flow meter’s range. These parameters indicate whether the flow rate falls within or outside the set ranges; they do not indicate that the electromagnetic flow meter has exceeded its measurement range. Instead, they represent percentages of the range set for the electromagnetic flow meter. It is important to note that this range can be adjusted, and sometimes this is done to improve the resolution of the signals output by the electromagnetic flow meter. Therefore, users can set the upper and lower flow limit alarms according to their actual measurement needs. If they deem it unnecessary, they can choose to disable these alarms; they are mainly used as a reminder for customers regarding specific flow rates. The specific solution is as follows: The upper and lower limit alarm signals indicate that either the output current, the output frequency, or the pulses are out of range. After increasing and decreasing the flow range, cancel the upper and lower limit alarms.