User Manual
Chapter 4
GFK-1742F
Jan 2020
Configuration
110
5.01 User Units, Counts. The User Units to Counts ratio sets the number of programming
units for each position feedback count. This allows the user to program the DSM314
in application-specific units. The User Units and Counts values must be within the
range of 1 to 65,535. The User Units to Counts ratio must be within the range of 8:1
to 1:32. For example, if there is 1.000 inch of travel for 8192 feedback counts, a
1000:8192 User Units: Counts ratio sets 1 User Unit equal to 0.001 inch. Default is
1:1.
The User Units to Counts ratio sets the number of position programming units for
each feedback count. It is a requirement to set this value correctly for the
mechanical systems coupled to the axis, otherwise movement to unsafe and
inaccurate positions may occur.
Note:
It is important to set this relationship at the beginning of the configuration session; most
other configuration fields are specified in user units.
For example, Velocity will be specified in user units per second and Acceleration will
be specified in user units per second per second.
This ratio is a very powerful scaling feature. A User Unit to Counts ratio can be
configured to allow programming in other than default counts. In a simplified
example, suppose an encoder feedback application has an encoder that produces
1,000 quadrature counts per revolution (250 lines) and is geared to a machine that
produces one inch per revolution. The default unit would be one thousandth of an
inch per count. However, you may want to write programs and use the DSM300
Series module with metric units. A ratio of 2540 User Units to 1000 Counts can be
configured to allow this. With this ratio, one user unit would represent .01
millimeters. 2540 user units would represent 25.40 millimeters (one inch) of travel.
The example below illustrates how to meet the requirements that the User Units and
Counts values be within the range of 1 to 65,535, and the User Units to Counts ratio
be within the range of 8:1 to 1:32.
The basic equation to satisfy is:
The numerator and denominator must each fit within the RANGE limits. The reduced
fraction must fit between the RATIO limits. The decimal point is always implied, not
used. The User Units to Counts ratio is always expressed as an integer ratio.
Sample Application
Use the User Units to Counts ratio to configure the DSM314 so you can program in
engineering units rather than encoder counts. As an example, assume a machine has
a motor with a motor-mounted quadrature encoder connected through a gear
reducer to a spur gear. The spur gear is mounted to the end of a pinch-roller shaft.
The pinch roller feeds sheet material for a cut-to-length application. The motion
program will specify the length of cut sheets. The programmer wishes to program
in 0.01-inch resolution.