According to different process equipment, pneumatic or electric actuators can be selected to form pneumatic ball valves and electric ball valves respectively. Pneumatic ball valves must be equipped with valve positioners to achieve proportional adjustment, and electric ball valves must be equipped with electronic electric actuators or servo amplifiers to achieve proportional adjustment.

3. Imperfect grounding is mainly affected by external interference such as pipeline stray current due to the influence of external interference and ground potential fluctuation. The electromagnetic flowmeter has good grounding protection. Generally, the grounding resistance is required to be less than 1000. Do not share the grounding with other electrical machines. Sometimes the electromagnetic flowmeter can work normally without grounding in good environmental conditions, but once the good environment does not exist, the instrument will fail, and then re inspection will cause more trouble. The change of the state of the electric equipment near the flow sensor (such as the increase of the leakage current) forms the ground potential change, which will cause the zero point change of the electromagnetic flowmeter.