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FM-4 Programming Module Reference Manual
Figure 39:
User Units View
Distance Group
Units Name
This is a 10-character name for the distance user units the user wants to use in the application.
Decimal Places
The number of decimal places set in this parameter determines the number of digits after the decimal point used in all distance
and position parameters throughout the configuration. Using a high number of decimal places will improve position
resolution, but will also limit the range of absolute position. You can select from zero to six decimal places of accuracy.
Note
When the number of decimal places are changed in an existing configuration file the Index accel and decel parameters
need to be checked.
Scaling
A Characteristic Distance and Length must be established to allow the FM-4 module to scale user units back to actual motor
revolutions. This scaling factor is as follows:
Characteristic Distance
This is the distance the load travels (in user units) when the motor travels the characteristic length (in motor revolutions).
Characteristic Length
This is the distance the motor travels (in whole number of revolutions) to achieve one characteristic distance of load travel.
Distance Scaling Examples:
A 1.5" diameter pulley is used to drive a conveyor belt, and the user wishes to use units of inches instead of revolutions.
Units Name — Set to Inches
Decimal Places — Set to desired accuracy 0.000
In one revolution of the motor (or pulley), the belt will travel a distance of one pulley circumference.
= 1.5" x π
44
Characteristic Distance
Scaling
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=
Characteristic Length
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