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Anti-Dither Module

Controller seeing too many counts?
Losing position in your control system?
High vibration environment causing false counts?

BEI's DIN rail mountable Anti- Dither module can help. By comparing the quadrature outputs on your encoder, the Anti-Dither Module can remove the unwanted part of the signal and give you a true picture of your system output.

The Anti- Dither module accepts quadrature encoder A and B signals and, through internal discrimination circuitry, passes the signals through only when there has been true movement of the encoder. This acts like 1/4 cycle of hysteresis and avoids encoder signal transition dithering due to mechanical vibration.

Idea for web processes, handling and inspection systems that use conveyors and simple speed control in applications that are subject to vibration.

Typical Applications

High Vibration Environment
Web processes, conveyors, in-line inspection stations, and heavy equipment operations are all subject to possible system errors caused by mechanical vibration. This can cause jitter or noise on the encoder signal and subsequent position and speed errors in the control electronics. The Anti- Dither Module, placed between the encoder and the receiving electronics, removes this type of error making sure the real data signal ends up at the controller.

Starts and Stops
In certain applications, such as conveyor systems or web processes, it may be necessary to stop the line to clear a jam or reset the process. There is no way to control where the encoder is in its output cycle when this occurs: it may have stopped at the rising or falling edge (a transition) of an output channel or somewhere in between.

When it stops on a transition, there can be ambiguity in the controller. The output of the encoder may dither from its HI state to its LO state due to mechanical noise in the conveying system. This fluctuation can be read as true motion in the controller. The Anti-Dither Module creates hysteresis so mechanical dithering does not create a false count.
Waveform Diagram
Operation of the Anti-Dither Function
Waveform Diagram Operation of the Anti-Dither Function Buy Anti-Dither Module
Note: Inverted channels, A/ and B/ have not been shown. Index or Z channel is also not shown in the above diagram but is passed through directly as an optically isolated signal and maintains its original relationship to the encoder output channel.