As the maintenance staff negligence, it may be that some sensor position errors, such as not in place, the sensitivity of sensor fault, fault etc.. Should always check the sensor sensing position and sensitivity, the deviation timely adjusted, sensor if broken, replace immediately. Most of the time, if in the guarantee power supply, pneumatic and hydraulic supply accurate, more is the problem of sensor fault. Especially the magnetic induction sensor, because of the long-term use, may well internal ground mutually stuck, unable to separate, usually closed signal, which is the common type of sensor, replaced only. In addition, the vibration of equipment, most of the sensor in the long-term use, will appear position loose, so in daily maintenance to regularly check the position of the sensor is correct, whether the firm fixation.