Common faults of photoelectric encoder and the solutions

by:HENGXIANG     2020-11-05
Photoelectric encoder detection device of transmitting and receiving device is installed at the scene of the production, has exposed many defects in the use, the internal factors and external factors, mainly manifested in the following aspects: 1. Launch device or accept device caused by mechanical vibration of displacement or offset, cause the receiver can not receive light signals, and does not produce electrical signals. Application of photoelectric encoder, for example, in the speed control system of steel rolling, for photoelectric encoder is bolted directly on the shell of the motor, photoelectric shaft through a hard spring leaf and motor shaft is connected, because the motor load is impact load, when the mill through the steel will cause the vibration of the shaft of the motor and the shell. Through determination, through steel electric encoder vibration velocity 2 time. 6 mm/s, the vibration velocity can damage the internal function of photoelectric encoder. Cause a false pulse, leading to the control system, unstable or misoperation lead to accidents. Improvement measures: changing the installation way of photoelectric encoder, photoelectric encoder is not installed on the motor shell, but on the basis of the motor to make a fixed bracket to independent installation of photoelectric encoder, photoelectric encoder shaft and motor shaft center must be in the same level height, two axis adopt soft rubber or nylon hose connection, to alleviate the impact load of the motor on the impact of the photoelectric encoder. Adopting this way after the vibration test, the vibration velocity dropped to 1. 2mm/s。 2. By photoelectric detection device is installed at the scene of the production, the production site environmental factors cause the photoelectric detection device can't work reliable. Such as installation of high temperature and high humidity, lead to the photoelectric detection device element characteristics of internal change or damage. In continuous casting machine to send dummy tracking system, for example, the position of the photoelectric detection device installed near the slab, caused by environment temperature high photoelectric detection device error signal or damage, caused the production or personal accident. Improvement measures: according to the model selection of the encoder site condition to choose suitable temperature of the encoder, the temperature must be in the encoder of the normal operating temperature range, and also it can be installed according to the encoder, plus a large cooling effect of the flange, without encoder directly on high temperature equipment surface, cooling. 3. Production site of various interference sources, interference of the photoelectric detection device, for the distortion in photoelectric detection device output waveform distortion, maloperation accident or production system. Photoelectric detection device is installed on production equipment, for example, ontology, the distance of the signal via cable transmission to be in commonly 20 m to 100 m, although transmission cables are generally choose multi-fiber shielding, but because of the cable conductor resistance and the influence of the capacitance of the line plus together and other cable laying, vulnerable to the influence of all kinds of electromagnetic interference, thus causes the waveform distortion, so that the signal of the feedback to the speed control system and the actual value of deviation, and to lower the system precision. Improvement measures: choose the photoelectric detection device output signal transmission medium, using twisted-pair shielded cable replace ordinary shielded cable. Twisted-pair shielded cable has two important technical features, one is the electromagnetic interference on the cable has strong protection ability, because the space electromagnetic interference current online can offset each other. Twisted-pair another technical feature of shielded cable is mutual ground after two line spacing is very small, two lines to interfere with the basic equal distance from line, two line is basically the same on shielding network of distributed capacitance, the common-mode interference suppression effect is more obvious. Twisted-pair cable, also is what we call cable, can be divided into shielded twisted-pair cable ( 屏蔽双绞线,stp) With the unshielded twisted pair ( 无屏蔽的双绞线,utp) , the so-called shielded twisted-pair cable is refers to between the twisted-pair and outer insulation sleeve has a metal layer houses. Shielding layer can reduce the radiation, prevent information eavesdropping, also can prevent external electromagnetic interference into, make the shielded twisted-pair cable than the same kind of unshielded twisted pair has a higher transmission rate)
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