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What are encoders? |
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All machine spindles or motor shafts count revolutions by translate electronic signals from sensors called encoders. |
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What kinds of rotary encoders are there? |
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Incremental Rotary Encoders: For each rotation a fixed signal from 0-1 will be sent out. Signals are evaluated by electronic counters.
Absolute Rotary Encoders: Within 360 degrees, every position has corresponding binary code such as BCD, or Gray code. (BCD, Gray Code must interface with counter/ numerical control or computer for information to be processed. Generally the cost with this type is higher than incremental encoders..........) |
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What functions do rotary encoder ABZ phases have? |
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If using to (check)calculate rpm, for example, on uni-directional shafts, the sensor only needs one channel output that’s enough.
Quadrature encoders use dual channel A and B phases differtial 90 electrical degrees. This type can be used to (recognition cw or ccw)differentiate direction on a rotating shaft as well as having the advantage of better accuracy during heavy vibrations.
The index Z phase will only out put 1 signal per revolution and is used to find the index or counts. |
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How should one select an encoder to use? |
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First, one must pay attention to shaft loading then decide encoder size.
Next, depend the mounting space and decide shaft or hollow type is appropriate, direct or indirect coupling.
Look at (accurate)precision needs realistically. Figure out ball screw pitch or roller diameter. Then decide what resolution(P/R pulse/revolution) requirements.
Calculate machine rpm and select frequency response range. F=rpm/60 x P/R
Will the encoder be paired with a counter, PLC, or computer? Decide on operating voltage.
Consider cost. |
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What should one pay attention to when installing an encoder? |
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The machine spindle or encoder shaft must be aligned with the center line.
Even without complete certainty, please install a coupling within both shaft. (Slight)Micro-angle deviations are allowable. Even if the deviation is too large, coupling will rupture no damage encoder.
If connecting the hollow type encoder, its weight has already been born by the mechanical axis. It only takes a spring to fix encoder unlikely to rotate.
Once the coupling is installed, first lightly use the back side of a ball pen to shore up coupling circumference and rotate by hand. See if pen is jig or not. If yes, continue with adjustments.
During installation, avoid hammering the encoder. |
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What if the counter does not count once the sensor is installed? |
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Make sure encoder is connected to the electricity and voltage is proper.
Ensure AB channel signal lines working.
If there is only a single channel output the encoder has broken down.
If the above mentioned are all correct the counter is (malfunctioning?). |
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What if the counter is inaccurate? |
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Check if the coupling is loose or not.
Remove the encoder from the machine. Make a mark on the shaft and rotate the shaft one full turn. Check if the counter shows the same as the P/R or not. Rotate the shaft back and forth several times making sure it still properly counts.
Sometimes the encoder cable and power wires are lay together. This can influence the waveform and cause counter inaccuracy.
Use an oscilloscope to check the waveform, see if there is any interference. If so install a surge killer or inductance to eliminate the interference. |
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How can one resolve malfunctioning imported rotary encoders? |
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It is best to ask the company that the machine was originally purchased from, unfortunately the time needed for this is comparatively long. If this solution doesn’t meet pressing needs, write down the voltage, resolution, shaft dimensions and output mode, and this company can look for a substitute or provide an overhaul. (Generally repair is not an option b/c obtaining parts is not easy.) |
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