Delta RMC101 - Manual (Page 588)

RMC100 and RMCWin User Manual
6-44
be 800 x 15 or 12000 quadrature counts for each revolution of the shaft B.
Notice that we could increase the position units to be 10,000ths of a revolution and still have
more counts than position units, but we will assume that the user really doesn’t want to use this
extra resolution. Increasing the position unit resolution would lower the maximum speed, as
speeds are limited to 65535 position units per second. Therefore, we can calculate our scale:
Next, we need to choose a Prescale Divisor. The largest of the valid divisors (1, 2, 4, and 8) that
can be multiplied by 2730.667 and still be within ±32768 is 8. When we multiply this divisor by the
scale and round it to the nearest integer, we get the following parameters:
Scale = 21845
Prescale Divisor = 8
In this case our effective scale is 2730.625 instead of 2730.667, which means our scale has an
error of 0.0015%.
See also:
Quadrature Overview
Quadrature Wiring
Quadrature Configuration
Quadrature LED Indicators
Quadrature Specifications
Quadrature Homing
6.3.8 Homing a Quadrature Axis
Quadrature encoders do not provide absolute position. To use a quadrature encoder in a position
application, a known reference position must be established. This position is called the Home
position. The process of moving the axis to find the home position is called Homing. As the
encoder is rotated it increments or decrements the position from the initial home position.
Each RMC quadrature axis has two inputs that can be used for homing:
• The index (Z) input comes from the encoder to indicate that the encoder has rotated a full
revolution.
• The home (H) input comes from a limit switch or proximity sensor.
Both the Z and H inputs must be active for the RMC to register an active Home. Therefore, if
either the Z or H input is not used, the input must be made active either by wiring or inverting the
Z or H input in the Config parameter word.
The RMC is commanded to wait for the Home condition by the Arm Home command. That RMC
axis is then said to be Armed. Unless the quadrature axis is armed, the Home condition is
ignored. If the Auto Home Re-arm configuration bit is set, the axis will automatically be re-armed
after homing. Otherwise, the Arm home command must be issued to arm the axis again after
homing.