Delta MMC120 - Manual (Page 23)

MMC120 Linear Motion Control Module Startup
Delta Computer Systems, Inc. 360/254-8688 23
SCALE Parameter (Default: 30300) Range: -32767 to 32767, excluding 0
The SCALE factor converts TRANSDUCER COUNTS to Position Units. The SCALE is defined as:
Position Units per Inch x 32768
SCALE =

x Sign
Transducer Cal. Number (
µ
s/in.) x 120 MHz
Where ' Sign' equals +1 when an extend move yields increasing ACTUAL POSITION, and -1 when an extend
move yields decreasing ACTUAL POSITION. An extend move always yields increasing TRANSDUCER
COUNTS, but the sign of SCALE determines whether extending the axis will give increasing or decreasing
ACTUAL POSITION.
The calibration number must be specified in the same base units as the Position Units (inches, mm, etc.).
Position Units are generally 0.001 inches or 0.1 mm. There are usually 1000 Position Units per inch when the
calibration number is in microseconds per inch.
OFFSET Parameter (Default: 0) Range: -65535 to 65535 position units
Next, the axis OFFSET must be set. The axis OFFSET is added to the position of the axis when the ACTUAL
POSITION is computed. When the OFFSET is changed make sure to change the EXTEND LIMIT and
RETRACT LIMIT by the same amount. Use the following equation to adjust the current ACTUAL
POSITION to be something else:
OFFSET = old OFFSET + DESIRED POSITION - ACTUAL POSITION
Both the EXTEND and RETRACT limits must be adjusted in the same way as the OFFSET, and another 'Alt-
P' command must be issued. Move the axis to the EXTEND and RETRACT limits and make any adjustments
necessary.
TRANSDUCER COUNTS
SCALE = -30,212
OFFSET = 25,000
EXTEND & RETRACT LIMITS
0
0
25,000
25,000
39,046
-36,000
-11,000
-11,000
0
0
RETRACT LIMIT = 20,000 EXTEND LIMIT = -6,000
-60,423
65,535
-35,423
-35,423
ROD LENGTH MAXIMUM COUNTS
Moving The Axis
With the axis drive output still disconnected and the transducer on, move the axis close to the physical extend
limit (move it either manually or with a 'diddle box') - be sure to leave some space for safety. If neither of these
movement options are usable to you, the following procedure uses DCS120 and the Open Loop mode to slowly
move the axis. (Remember: extending is the direction that returns increasing TRANSDUCER COUNTS.)