Emerson FM-3 - Manual (Page 53)

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Setting Up Parameters
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 software. 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-3 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
= 1.5 x 3.14...
= 4.712 inches / revolution
Scaling
Characteristic Distance
Characteristic Length
------------------------------------------------------- =
Scaling
Characteristic Distance = 4.712
Characteristic Length = 1
--------------------------------------------------------------------------- =