Encoder Failure Analysis and Encoder Replacement

Encoder Failure Analysis

Absolute encoder battery voltage drop: this kind of failure usually has the meaning of clear alarm, this time need to replace the battery, if the reference point position memory is lost, but also must perform to return to the reference point operation control. Encoder installation installed after the reduction gear, such as the shaft end of the winch wire rope reel or the last section of the reduction gear shaft end, this method has no gear back and forth clearance, the measurement is more direct, higher precision, this method is generally measured in long-distance positioning, such as a variety of lifting equipment, feeding trolley positioning, and so on.

Failure of the encoder connection cable: This type of failure is the most likely to occur and is often encountered during maintenance and repair, and should be a priority. Usually for the encoder cable break, short circuit or poor contact (line loose), then need to replace the cable or connector. Should also pay special attention to whether it is due to the cable is not fixed tightly, resulting in loose caused by open welding or broken circuit, then need to tighten the cable.

Encoder +5V power drop: is the +5V power supply is too low, usually can not be lower than 4.75V, caused by low power supply failure or power transmission cable resistance value is large and caused by loss, then need to overhaul the power supply or replace the cable.

Failure of the encoder itself: This refers to the failure of the encoder's own components, resulting in its inability to generate and output the correct waveform. In this case, the encoder needs to be replaced or its internal components repaired.

Encoder cable shielding wire is not connected or off: this will introduce interference signals, making the waveform unstable, affecting the accuracy of communication, must ensure that the shielding wire reliable welding and grounding.

Loose encoder installation: This kind of fault will affect the position control accuracy, resulting in stopping and moving in the position deviation amount of super poor, or even just turn on the servo system overload alarm, please pay special attention.

Grating contamination which will make the signal output amplitude drop, must use degreasing cotton with anhydrous alcohol to gently wipe off the oil stains and dirt. Absolute encoder is widely used in water conservancy, light industry, machinery, metallurgy, textile, petroleum, aviation, navigation and other industries. Specific to the project category such as: rotary table, gate opening, valve opening, hoist crane positioning, traveling crane positioning, level measurement, missile launch angle positioning, missile air rudder measurement, electronic latitude and longitude and other high-precision measurement and positioning occasions.

Encoder ReplacementMethods and Precautions

When the rotary encoder failure damage we need to find a new rotary encoder to replace it, then the correct replacement method do you know today, to talk about the replacement of rotary encoders and attention to the place.

revolveEncoder ReplacementSteps.

The first step is to remove the back cover of the motor and the encoder;

Loosen the encoder mounting screws.

In the third step, rotate the rotor shaft of the motor so that the mark on the encoder rotor coincides with the mark on the encoder housing;

Step 4: Remove the encoder, and pay attention to use special screws to avoid damaging the encoder;

Step 5: Rotate the new encoder so that the two marks of the encoder coincide;

Step 6: Install the encoder in the reverse order of the above;

Things to keep in mind during the replacement process.

1. During the installation of the encoder, make sure that the rotors of the motor are different, otherwise the relative position of the rotors will be lost.

If the relative position is lost, the old motor will need to use an oscilloscope to adjust the encoder mounting position, the new motor can be based on the motor rotor shaft mark to determine the adjustment of the encoder mounting position, that is, can be adjusted mechanically, you can also adjust the drive parameter MD1016 to set a bias value, but the method can only be used on the 840D.

2. Change the encoder to note that the encoder installed after the fixed screws, be sure to coupling on the top wire loose to eliminate the assembly stress caused by the phenomenon of jamming, rotate by hand after the top wire in the top of the dead.

3. Need to pay attention to the encoder wiring order, the reverse may run overcurrent fault. The signal output of the rope displacement sensor is divided into digital signal output and analog signal output, digital output type can choose incremental rotary encoder, absolute encoder, etc., the output signal is a square wave ABZ signal or Gray code signals, the stroke can be done up to 10,000 mm, linear accuracy of up to 0.01%, the resolution according to the different configurations of the maximum can be up to 0.001 mm / pulse.

Encoder installation high-speed end installation: installed in the power motor shaft end, this method has the advantage of high resolution, due to the multi-turn encoder has 4096 turns, the number of motor turns in the range, can be fully used to improve the resolution of the range, the disadvantage is that the movement of the object through the deceleration gears, the back and forth with the gear lash error, generally used for unidirectional high-precision control and positioning, such as rolling rolls in the roll gap control. In addition, the encoder is directly installed in the high-speed end, the motor jitter must be small, otherwise it is easy to damage the encoder.