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Appendix D. Operation

D.1 Quadrature encoder introduction

In typical closed-loop control systems, also know as servo system, the

encoder interface senses motor position and sends a position signal to

the controller. The diagram below shows a typical servo system.

The encoder generates pulses which indicate the shaft position. The

encoder output includes two signals, commonly called channel A and

channel B, which generate N pulses revolution. The two signals are

shifted by a quarter of a cycle, as shown below. The shift between the

two signals enables the controller to determine the direction of rotation,

depending on whether channel A leads channel B or vice versa.

MICROCOMPUTER

BUS

HOST

CPU

PCI-1784

ENCODER

CARD

QUADRATURE

ENCODER

(MOTOR)

QUADRATURE

SIGNAL

PHASE A

PHASE B

INDEX

QUADRATURE

SIGNAL

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 57

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Advantech PC-LabCard PCI-1784 Specifiche Pagina 51