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Pulse encoder principle and fault analysis!

When the circular grating rotates with the working axis, the light penetrates the linear part of the two gratings, forming the stripe between light and dark.These light and dark signals are received by the photoelectric element and converted into alternating electrical signals.The electric signals are two groups of current signals A and B, which are similar to sinusoidal waves, as shown in the figure below.A and B signal phase difference of 90°, after amplification and shaping into A square wave.The signal that passes through the two gratings, together with a "pulse per revolution", called a Z-phase pulse, is also processed as described above.The Z pulse is used to generate the reference point of the machine tool.Later pulses are sent to the counter, and the rotation Angle and speed of the shaft can be measured according to the number and frequency of the pulses.Its resolution depends on the number of turns of the circular grating and the subdivision multiple of the measuring line.

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Fault analysis of pulse

(1) Failure of the encoder itself: it refers to the failure of components of the encoder itself, resulting in its failure to generate and output correct waveform.In this case the encoder needs to be replaced or its internal components repaired.

(2) connection cable fault: This kind of fault is most likely to occur, which is often encountered in maintenance and should be a priority factor.It is usually the encoder cable break, short circuit or bad contact, then need to replace the cable or connector.Special attention should also be paid to whether the loose cable caused by loose welding or break, in this case the cable should be tightened.

(3) Pulse encoder +5V power drop: it means the +5V power is too low, usually no lower than 4.75V. The cause of the low is the power supply failure or the loss caused by the high resistance value of the power transmission cable. In this case, the power supply needs to be repaired or the cable needs to be replaced.

(4) Battery voltage drop of : This kind of fault usually gives a clear alarm, and the battery needs to be replaced at this time. If the memory of reference point position is lost, the operation of returning to reference point must be performed.

(5) The shield wire of the encoder cable is not connected or falls off: interference signals will be introduced, which will make the waveform unstable and affect the accuracy of communication. Therefore, reliable welding and grounding of the shield wire must be guaranteed.


(6) Loose encoder installation: This kind of fault will affect the position control precision, resulting in the position deviation in the stop and movement out of tolerance, and even the servo system overload alarm immediately after starting up, please pay special attention.

(7) Grating pollution will reduce the amplitude of signal output, so the oil must be gently wiped off with absorbent cotton dipped in anhydrous alcohol.



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