17
User Manual
Model PCS
Pneumatic Motion Control System
PTF rotary actuators less than 180 degrees of rotation
Considering all feedback potentiometers used on PTF rotary actuators have an electrical rotation angle of
340 degrees, and that the Zero and Span adjustments can only be adjusted down to a 50% window of total
electrical span, PTF rotary actuators less than 180 degrees of rotation will not be able to use the full scale span
of the analog command input signal, and will be treated by the Main Control as though they are 180 degree
units.
PTF’s less than 180 degrees of rotation are shipped with the feedback potentiometer’s electrical zero set to the
PTF’s rotational zero position, so when the zero analog command input signal is applied to the PCS input, the
PTF should be very close to the zero rotational position when the zero adjustment is fully CW.
Now follow the steps below.
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. This should only be a minor adjustment.
If the zero potentiometer needed many turns of adjustment, the PTF feedback potentiometer located on the
back of the PTF may be set incorrectly, and may prohibit the Span adjustment from being made properly. We
will address this in the Span adjustment section if necessary. (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 rod or towards 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.
Note: If the system does not move at all, go back and check all of your connections. For Option-N
models, be sure the valve cables are connected properly. If the wires are reversed, the actuator may
move opposite of the intended direction. (i.e., zero will move the actuator to its full scale position. If
the actuator does this, reverse the white wires from the valve cables.)
Also - If the LED’s occasionally pulse on, it may indicate a slight leak in the system. The system
will work OK with a slight leak, but you may want to eliminate the leak so the system operates at
maximum efficiency
