The principle of pressure transmitter is based on the total flow measurement instrument of Faraday current rotameter, so it is very important to ensure its measurement, proper installation, reasonable use and normal maintenance.

Some of the common failures in the application of pressure transmitters are caused by the destruction of electronic devices of instruments, some are caused by improper use, improper installation, natural environment, and hydrodynamic characteristics, such as the fluctuation of display information, the reduction of precision and even the destruction of instruments. It is generally divided into two categories: installation and regulation of the fault and all normal operation of the fault.

2. Common failure of pressure transmitter: electronic flowmeter manufacturers, especially for the coaxiality error of caliber steam flowmeter, will cause measurement deviation. When installing, it is necessary to consider that the front connecting pipe section L1 ≥ 6dn, the rear connecting pipe section L2 ≥ 2DN, DN is the hose diameter; do not install the regulating valve upstream and downstream of the instrument, and the pump source cannot be installed in the upstream and downstream to ensure the measurement precision of the instrument. Suitable for connecting cable, when measuring low conductivity medium and applying long-distance separated pressure transmitter, it is necessary to check the matching data chart, and make sure to use communication cable and excitation regulator wire with appropriate section.

2.1 failure during adjustment

2.1.2 natural environment

2.1.1 the installation fault occurs in the installation and adjustment link, and the flowmeter price is not easy to occur again and again under the same standard. This kind of fault is caused by improper installation, natural environment and hydrodynamics.

This kind of fault is caused by the influence of stray electric flow of pipeline, strong radio wave in indoor space, electromagnetic field of large and medium motors, etc.

Generally, excellent independent protective grounding is adopted, and the grounding device shall not be mutually grounded with other driving force switching power supply. The resistance of the grounding wire shall be less than 10 Ω, so as to improve the anti-interference ability of the instrument. However, in case of strong stray current flow, other countermeasures and insulation layer of total flow sensor and pipeline shall be selected. The influence of radio wave in indoor space is generally introduced by communication cable, which should be shielded by single or double layers, so the installation site should minimize strong vibration and strong magnetic field of AC and DC power supply. If necessary, add supporting points on the upper and lower sides of the measuring tube, and the allowable vibration level shall be less than 2.3g, and within the range of 20hz-50hz. It is not necessary to expose the instrument to the sun immediately. Protective cover shall be provided at necessary places.

2.1.3 hydrodynamic characteristics

Generally, it is caused by the wrong installation position, such as the height of the pipe installed in the pipeline easy to gather steam body or the vertical pipe section installed from top to bottom. Exhaust will occur; or there will be no back pressure behind the sensor, and the fluid mechanics will enter the air directly, resulting in the measurement tube is not full. The sensor shall be installed as perpendicular as possible, so that the measured medium flows through the instrument from top to bottom; when it is required to be installed horizontally, it shall be parallel to the road surface with the electrical grade center line. Prevent the sensor from being on the upper position of the pipeline and avoid the accumulation of bubbles at the electric stage. Both installation methods shall be provided with bypass and gate valves on both sides of the sensor for the convenience of instrument maintenance. In addition, the sensor and

The measured liquid contains fine bubbles with uniform distribution, which is not easy to endanger all normal work of the pressure transmitter. However, with the expansion of the bubbles, the output of the instrument will fluctuate, if the bubbles are large enough to be covered

When covering all the surface layer of the electric stage, the output data signal will fluctuate more because of the short circuit fault of the bubble passing through the control circuit of the electric stage.

When the pressure transmitter of the high-frequency waveform excitation regulator measures the slurry with too many solid components, the slurry noise will also be caused and the output data signal will fluctuate.

When measuring the mixed medium, if it enters into the total flow sensor to carry out measurement before mixing is not even, it will also cause fluctuation. Improper selection of metal electrode and measured medium will also endanger all normal measurement due to oxidation or electrode condition. Therefore, metal electrode should be properly selected according to instrument or relevant guidelines. It should not only consider that the metal electrode conforms to the corrosion regulations of the tested medium, but also consider that the surface layer of the electrical grade does not cause chemical changes, such as no passivation treatment, air oxidation, electrode, bubble and crud layer. The measuring medium shall be consistent with the raw material of the measuring tube gasket, so that the gasket can achieve corrosion resistance and necessary wear resistance, so as to improve the service life of the sensor. 2.2 failure during operation

This kind of fault is caused by the adhesion layer in the inner cavity of the total flow sensor, severe lightning strike and environmental damage. The most important thing is to analyze the fault of the instrument itself.

2.2.1 inner cavity adhesion layer

Because the pressure transmitter is often used to measure the stain hydrodynamics, after a period of operation, the accumulation of adhesion layer in the inner cavity will cause failure, which is caused by the large or small conductivity of the adhesion layer. If the accessory is cable sheath, the electric level control circuit will be short circuited, and the instrument cannot work normally. If the conductivity is obviously higher than that of hydrodynamics, the electric level control circuit will have short circuit fault, and the instrument can not work, so the adhesion layer should be eliminated.