Delta MMC120 - Manual (Page 85)

MMC120 Linear Motion Control Module Appendix A: DCS120
Delta Computer Systems, Inc. 360/254-8688 85
Open Loop Command
CAUTION: OPEN LOOP MODE DISABLES ALL SAFETY CHECKS OF THE MOTION CONTROL MODULES!
USE THIS COMMAND WITH CARE!
You can execute the "O" (open loop) command by pressing Alt-Shift-O or entering the ASCII value for O (decimal 79)
in the COMMAND field. (First you must specify the millivolts of drive output required in the COMMAND VALUE
field.)
Readback and Write Mode Toggle
Ctrl-T toggles between the Readback and Write modes (‘R’ or ‘W’ is displayed at the right end of the input line). When
in the Readback mode, the Command parameters on the DCS120 screen are red, and all fields are continuously updated
from the module. This mode is useful for observing the operation of the Programmable Controller or Bus Master.
When in the Write mode, the control parameters are not updated unless a parameter error occurs; when values are
entered from DCS120 they overwrite the values written by the Programmable Controller.
SCALE & OFFSET Calculation Commands
The P0 and P1 commands provide an easy way to set the motion controller's Scale and Offset parameters. To use these
commands, you must know the physical distance and the corresponding number of the transducer COUNTS at two
points. Measure the physical distance in position units (for example, thousandths of inches, millimeters) while noting
the corresponding COUNTS on the DCS120 main screen. Once you have these numbers, simply enter the "zero"
position information using P0 and the other position using P1.
For example, if at position 0 the actual position is 0.000 inches and the COUNTS are 2163, then enter:
P0 0 2163. If at position 1 the actual position is 27.500 inches and the COUNTS are 31626, then enter:
P1 27500 31626.
Note: If the COUNTS are not entered, the current value in the COUNTS field will be used.
After you enter values for both P0 and P1, the SCALE and OFFSET fields will be updated on the screen (notice the
parameters turn gray). Use the Alt-P command to activate the newly calculated numbers. (In the above example
SCALE changes from 32767 to 30564 and OFFSET changes from 0 to -2018.) The RETRACT and EXTEND LIMITS
are updated to their new actual positions using the new SCALE and OFFSET values.
OFFSET Parameter
The OFFSET and other parameters may be displayed incorrectly on the DCS120 screen under some circumstances.
This is because the offset and retract limits specify the zero location of the axis. The numbers are not necessarily
incorrect (the module still functions correctly), but they may not look right. To correct the problem simply enter the
correct value for the Offset and save the parameters to a file (using the S filename command). Whenever you start
DCS120, read the file (using the R filename command) and DCS120 will display the parameters correctly.
Variable Datalogging Rates
The Plot Time (on the main parameter screen) shows the time base of the graphic display; it can be changed with the T
n command, where n is the time in milliseconds. Each axis is set independently. For example, if you set this field to
10 on axis 1, the plot will represent 1024 samples of 10ms each (10.24 seconds of motion). The default time is 1
millisecond.