In a world where accuracy is paramount, reducing electrical noise between your encoder and your motion controller is essential. The main AC power supply, electrical motor cables, solenoids, fans, relays, fluorescent lighting, or a host of other sources, can cause this common noise problem. The key to assuring accurate motion control through the electrical signals of your encoder is by keeping down the noise!
Differential signals may be one answer to the problem of keeping down the noise, and are almost a necessity when you are dealing with long cable lengths of 30 feet or more. With differential signals, each signal from your Accu-CoderTM is “split” into two signals that are exactly 180 degrees out of phase with each other. These signals are called complimentary signals, because one is the mirror image of the other. Because differential input circuits sense the differences between two signals, and electrical noise usually appears the same on both signals (referred to as common mode noise), this type of noise is rejected by the input circuitry. To properly read the differences between signals, your Accu-CoderTM must have a line driver “HV” or “H5” output circuit, and your motion controller must have a differential input. Differential signals are becoming more popular, due to the speed at which they can provide accurate measurement, and help to minimize problems associated with electrical noise.
Besides differential signals, the following basic installation practices may help to reduce electrical noise:
-- Always route power and signal lines separately.
-- Avoid splices and junctions between the encoder and the controller/counter.
-- Signal lines should be twisted and shielded, placed 12” from other signal lines, especially power.
-- Provide clean power to your equipment and your encoder. +/- 2%
-- Avoid the use of excessive cable length.
-- Properly ground all motors, gears, shafts, and equipment.
-- The encoder cable shield should only be connected at one end. Preferably the controller/counter end.
-- Use differential driver signal outputs with high quality twisted shielded pair cable.
Encoder Products Company’s friendly sales staff can help you with any technical questions for your specific situation, regarding line driver outputs, and reducing electrical noise.
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