AXIOMTEK MIRU130, User Manual

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Machine Vision MIRU130 Board
Operating 29
Chapter 4
Operating
4.1 Operating
This section describes the detail operation of the MIRU130 vision I/O feature.
4.1.1 Encoder function
The MIRU130 vision I/O feature supports 1CH 16-bit incremental quadrature encoder
input for the AB signal mode, which is used for applications where direction sensing is
required. This mode consists of two square-wave pulse signals known as Phase A and
Phase B generated by a rotating encoder. Phase A and Phase B signals are coded 90°
out of phase from each other
—Phase A is either 90° phase leading or lagging behind
Phase B. The MIRU130 is able to count square-wave pulses of Phase A and Phase B,
and then determine rotating direction of motor movement by comparing the phase
relationship between Phase A and B:

When the quadrature encoder is rotating in a clockwise direction, its signal will
show a positive direction of Phase A leading Phase B.
 When the quadrature encoder rotates counterclockwise, its signal will show a
negative direction of Phase A lagging behind Phase B.
Besides direction, the quadrature encoder can generate another signal named Phase Z,
which is produced once per complete rotation of the quadrature encoder. Phase Z is
used by the MIRU130 baord to locate a specific position when the quadrature encoder
completes a 360° rotation, so that the board can reset its counter value to zero if
necessary.
In most cases, the x4 Phase AB signal mode is applied to incremental encoder devices.
For example, an incremental encoder generates 1000 pulses per phase (A or B phase)
when a motor completes a 360° rotation, but the count will show 4000 pulses.