ANTI-DITHER ELECTRONIC MODULES Introduction This interface module uses the position information in a dual channel quadrature encoder to remove spurious counts caused by mechanical vibration. Logic gates in the Anti-Dither Module use the quadrature relationship to discriminate between dithering and actual movement. Using this quadrature relationship of the data, a signal is created with +/- 1/4 cycle of hysteresis. The index pulse from the encoder is optically isolated and passed directly to the controller for use as a reference. WHY USE AN ANTI-DITHER MODULE CASE 1 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 vibration 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. CASE 2 HIGH VIBRATION Another situation arises where the end use involves very high vibration construction machinery or mill duty applications for example. This is especially true when the encoder is being used as a single channel tachometer. In this instance the encoder output can have a vibration signal superimposed on the data channel, leading to multiple transitions on every cycle. This effect can be eliminated in the controller by using an encoder with dual channels in quadrature along with an Anti-Dither module. In this case, the Anti-Dither module can clean things up. WAVEFORM DIAGRAM Illustrating Operation Of The Anti-Dither Function Note: For simplicity of illustration, the inverted channels, A/ and B/ have not been shown. The index, or Z, channel is also not shown in the associated diagram but is passed through directly as an optically isolated signal and maintains its original relationship to the encoder output channel. Reference Optical Isolator Module data sheet for connection diagrams. Page 1 Copyright 2019 Sensata Technologies, Inc. www.sensata.comExample: EM-DR1-AD-24-TB-28V/V ORDER OPTIONS Use this diagram, working from left to right to construct your model number Note: Refer to BEI Opto Isolator Module Applications guide for mechanical specifications and connection instructions. EM DR1 AD - 24 - TB 28V/V - - EM: Electronic Module DR1: 114.5mm X 99mm X 22.5mm DIN Rail Package AD: Anti-Dither Function Output from Encoder 5: 5VDC 15: 12-15 VDC 24: 24VDC TB: Terminal Block Supply Voltage/Output from AD Module 28V/V: V = V out in 28V/5: V = 5 VDC out 28V/OC: V = Open Collector out AGENCY APPROVALS & CERTIFICATIONS Page 2 Sensata Technologies, Inc. (Sensata) data sheets are solely intended to assist designers (Buyers) who are developing systems that CONTACT US incorporate Sensata products (also referred to herein as components). Buyer understands and agrees that Buyer remains responsible for using its independent analysis, evaluation and judgment in designing Buyers systems and products. Sensata data sheets have Americas been created using standard laboratory conditions and engineering practices. Sensata has not conducted any testing other than that +1 (800) 350 2727 specifically described in the published documentation for a particular data sheet. 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