8
User Manual
Model PCS
Pneumatic Motion Control System
The following formula will translate the voltage reading into the Decel Range.
DR = 0.01485 * V * t
where:
DR
= decel range
V
= voltage reading from the PCS
t
= full scale travel of the actuator (Note: for PTF rotary actuators with total rotation less than 180º,
always make t = 180)
Example 1:
If the Decel Range is set to 5 volts for an 8 inch stroke cylinder, then deceleration will occur for 0.60
inches (0.0149 * 5 * 8).
Example 2:
If the Decel Range is set to 5 volts for a 180º rotary actuator, then deceleration will occur for 13.4º
(0.0149 * 5 * 180).
CURRENT POSITION
Current Position is a 0 to 10 volt output signal that mirrors the feedback signal from the actuator, fully scalable
with the Zero and Span adjustments. In other words, its output will always be 0 to 10 volts no matter how Zero
and Span are adjusted. It can be used to monitor the motion of the actuator and the output may be sent to a
calibrated display.
AT POSITION (@ POS)
At Position is a digital output signal that is normally open and switches to ground when the actuator is within the
Deadband zone. This signal is useful for utilizing a PLC I/O card to receive a signal indicating that the actuator is
within the Deadband zone, potentially eliminating the need for an analog input card.
REPEATABILITY AND STABILITY
It is important to understand the difference between repeatability and stability. A system is considered
repeatable if it comes to a stop inside the deadband zone. A system is considered stable if it comes to a stop
in the deadband zone time after time with no overshoot. There are different degrees of instability. The first is a
system that approaches the commanded position and overshoots it just a little and has to reverse itself before
settling to a stop in the deadband zone. This level of instability may be acceptable in many applications. The
worst type of instability is oscillation around the deadband zone, never settling to a stop. This level of instability
must always be resolved.
MOVEMENT DIRECTIONS
Movements of the actuator may be described as “Increasing” or “Decreasing.” An “Increasing” move is one that
moves toward the Full Scale Position. A
“Decreasing” move is one that moves toward the Zero position.
!
Be cautious when utilizing the @ POS signal. If there is overshoot in the application, the actuator may
momentarily go through the Deadband Zone, causing the @ POS signal to momentarily transition
back open, before finally stopping in the Deadband Zone.
