ABB CM30 User Manual page 23

ControlMaster CM30 and CM50
Universal process controllers,
...Basic
Loop 1 (2) Mot Valve
Motorized Valve Output With Feedback
SPT
PID
PV
Motorized Valve Output Without Feedback (Boundless)
A motorized valve output without feedback (boundless) process controller provides an output that is effectively the
time derivative of the required regulator position (the controller signals the regulator, not where to go to [position
derivative], but in the direction to travel and how far to move) by a series of integral action pulses. Therefore, the
controller does not need to know the absolute regulator position and is not affected when the regulator reaches the
upper or lower limit, as determined by the regulator's limit switches (hence the term 'boundless').
When a deviation from setpoint is introduced, the regulator is driven for a length of time equivalent to the proportional
step. The regulator is then driven by integral action pulses until the deviation is within the deadband setting.
Control
Deviation
IM/CM/ED–EN Rev. B
1 1
/ and / DIN
4 2
(OP x Ratio) + Bias
Raise
Time 
Proportional
Lower
Step
Open Relay
Motorized
Valve
Controller
Close Relay
Position Feedback
Integral Action Pulses 
Proportional Integral Action
Step
6 Basic Level
Time 
Pulses
21