Bimba PCS - Manual (Page 16)

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12. COMMAND THE BIMBA ACTUATOR TO ITS ZERO POSITION
We will command the PCS to move to different positions by adjusting the
command signal input to TB4. First command the PFC cylinder or the PTF rotary
actuator to retract to the zero position by setting the analog command input signal
to 0 volts or 4 mA, depending on the setting of jumper J01. Either the cylinder
will move to its hard stop (either internal or external) or it will move to a point
short of that stop.
Note: Improve performance by not using the actuator end of stroke
limit as a hard stop. (Eliminates any potential stiction between the
actuator piston and the end cap, as well as improves the positioning
capability at end of stroke or rotation). This can be accomplished by
implementing mechanical hard stops in the application fixturing or
by using command signals greater than the set zero position or less
than full scale.
13.
PRELIMINARY “ZERO” ADJUSTMENT
PFC and PFCN cylinders and PTF rotary actuators greater than 180
degrees of rotation (See below for PTF’s less than 180 degrees)
Adjust the Zero setting so that it coincides with the desired retracted or rotational
position hard stop. First note the two red and green LEDs on the PCS printed
circuit board. If the PCS wants to move the actuator towards the actuator zero
position, but cannot due to a mechanical limitation, the red LED will stay on
continuously flicker. Look at the LEDs and make the adjustments described in
one of the two following paragraphs.
If the Red LED is On - (The Zero setting is currently set beyond the desired
retracted or rotational position). Adjust the Zero potentiometer CCW slowly, until
the red LED goes off. (If the zero potentiometer was adjusted too far and the
actuator moved away from zero, adjust the Zero potentiometer CW just enough to
move the actuator back to the zero position. If adjusted too far, the red LED will
come back on). Both LEDs should be off when set correctly. This ends the
preliminary Zero adjustment.
If Both LEDs are Off - (The Zero setting is currently set somewhere in mid-
stroke.) Slowly adjust the Zero potentiometer CW to move the actuator toward the
zero position. The red LED will flicker while being adjusted. When the actuator
hits the zero position, the red LED will continue to flicker even when the
adjustment is no longer being turned. Now adjust the Zero CCW just enough to
turn off the red LED. Both LEDs should be off when set correctly. This ends the
preliminary Zero adjustment.