Merck Millipore Mobius Chrom 20 System User Manual page 166

166 User Guide
The Loop Tuning popup shows the control loop values on a chart and allow to tune the control
parameters in order to reach the desired dynamic properties. Ramp rate is used outside the
window covered by the PID control loop.
Fixed speed (Non PID controlled mode): the pump speed shall ramp until the speed setpoint is
reached.
Flow and linear velocity (PID controlled mode): the control loop will compute a pump speed
setpoint using PID parameters to reach the Flow setpoint entered by user. First, the pump speed
shall ramp until the flow is within a configurable Control deadband (percentage of the setpoint).
Once within the control deadband, the PID loop shall begin controlling the pump speed.
"Loop within deadband" status is enabled and the stability timer is latched. When the stability
timer reaches stability time, "Stable status" is enabled. The PID Loop controls pumps speed,
proportionally to the error between the measured pump flow and the flow setpoint. When the
flow reaches the setpoint within the PID deadband, the controller will freeze the speed setpoint,
to avoid micro oscillations. It will unfreeze and be back to PID control as soon as the flow is out
of the control deadband. If Flow Setpoint is modified, the pump speed will ramps up/down at
ramp rate until Flow is within Control Deadband.