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Vortex flowmeters encounter certain operational issues when measuring coke oven gas; below we will analyze the factors behind these issues and the solutions for them. The factors that cause problems in the on-site measurement system can be summarized into two main categories: 1) those caused by the flow meter or its associated equipment; 2) issues related to the flow meter itself – that is, when the flow meter is functioning properly but problems arise due to environmental or systemic factors, and such factors are relatively difficult to identify. In addition to requiring technicians to be familiar with these surface properties, they also need to possess extensive knowledge of surfaces as well as rich field experience in order to conduct analyses, make inferences, and perform various experiments before reaching a conclusion. Some problems still arise from some unexpected situations. Problems that are not related to the flow meter usually manifest as an unstable output signal. Based on practical experience, when using vortex flowmeters to measure coke oven gas, the factors that cause unstable output signals include the following: 1. It is well known among users that vortex flowmeters are not suitable for use in environments with strong vibrations; however, in situations where the magnetic field changes frequently, the vortex flow sensor is also disturbed, resulting in signals that are higher than normal. Practice has shown that in sites without gas activity, when a vortex flow meter is placed in a changing magnetic field, at the moment the magnetic field changes, the meter generates an error signal. Once the change is complete and the meter is again in a stable magnetic field, it will output normal signals. 2. Since coke oven gas contains many impurities that tend to crystallize, these impurities accumulate on the sensor head, resulting in inaccurate measurement by the flow meter. When temperature is increased, impurities evaporate, which increases sensitivity and thus enhances the signal; conversely, the signal decreases, leading to unstable data. 3. Since coke oven gas has a high temperature and high humidity at the time of production, moisture is present during its transportation. Gas movement causes the water content to fluctuate back and forth, thereby creating a pulsating flow. When in such a fluid condition, the vortex flow meter outputs data that fluctuates greatly, making it impossible to reflect the actual production conditions. 4. Inadequate compression of the wires during external wiring leads to intermittent signals during transmission. 5. The external ground wire does not meet the standard requirements, which allows 50Hz interference from high-voltage currents to enter. When the normal signal frequency is higher than 50Hz, the output signal is normal; otherwise, an error signal is generated. Solution: 1. During the installation of the vortex flowmeter and the connection process, it is necessary to ensure accuracy at every stage, including site surveys prior to installation, wiring of the components during installation, and system grounding, so as to guarantee that accurate data is detected and can be output precisely. 2. Regarding the measurement systems in operation, the approach of \"dual-track measurement with comparative recognition\" as well as the \"substitution method\" can be used to identify and resolve faults in the measuring instruments in use. 3. Drain the pipes at regular intervals, especially to remove moisture from the sections ahead of the straight pipe sections. Assign a dedicated person to carry out this task on a scheduled basis, in order to minimize the amount of moisture in the measurement sections and eliminate fluctuations in the fluid as much as possible. 4. Clean the vortex flow meter regularly as a whole; if necessary, blow through some of the external sensors to prevent impurities from accumulating there. In cold seasons, installing heating devices on the straight sections of the pipeline as well as on its exterior can also help reduce the accumulation of impurities at the vortex flow meter. Schematic diagram of the signal processing circuit for conventional vortex flowmeters: sensing element → preamplifier → low-pass filter → integrator → pulse signal, or → D/A converter → 4–20 mA output. Different detection elements have different characteristics, so different pre-amplifiers should be selected. The initial signal from the sensing element of the vortex flow meter is amplified by a preamplifier, which increases the amplitude of the signal; at the same time, the noise components present in the signal are also amplified. To extract the true signal, it is necessary to filter the signal. The sources of noise in vortex flowmeters include the following: 1. Fluid flow noise; disturbances caused by improper installation of the vortex flowmeter; secondary flows; and noise generated by pulsating flows. Relying solely on signal processing is insufficient to resolve the issue completely; the fundamental solution is to choose an appropriate installation location ； 2. Noise generated during vortex separation: During vortex separation, in addition to the main vortex, sub-vortices with frequencies equal to 1/5 to 1/10 of that of the main vortex are also generated. These are interference signals that become particularly noticeable at high flow rates ； 3. Signal fading or intermittent interference: This is caused by an improper design or poor assembly of the transmitter, or by dirt accumulating on it during operation, which leads to deformation of the transmitter. This leads to unstable vortex separation, poor axial synchronous separation, and twisted vortex lines; in terms of the signal waveform, this manifests as leakage waves or a poor regularity in the waveform ； 4. Mechanical vibration interference: The vibration noise generated by pipeline vibrations is transmitted to the preamplifier, causing severe interference with the vortex street signal ； 5. Electromagnetic interference noise: Strong electromagnetic field signals in the workplace can interfere with the proper operation of vortex flow meters. After filtering, the signal from the vortex flow meter is converted into a square wave pulse signal by a shaping circuit. Or, after D/A conversion, it outputs a standard 4–20mA analog signal.