NEW BRUNSWICK SCIENTIFIC BioFlo 4500, Manual To Operations

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New Brunswick Scientific Co., Inc. User’s Guide
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NOTE:
The following procedures refer only to the use of the BioFlo 4500
equipped with the ML-6100 controller .
A cascade
is a control scheme in which the output of one control loop influences
the setpoint of one or more other loops. In other words, it uses one parameter to
influence others. For example, if the Dissolved Oxygen (DO) control loop is
cascaded to Agitation, whenever the DO current value drops below its setpoint
causing an increase in DO control loop output, the agitation setpoint will increase.
This is effective, because agitation strongly influences DO. With this type of
cascade, errors in DO are corrected by changes in agitation RPM.
This controller allows cascading from any loop to as many as five other loops.
Dissolved oxygen is the most commonly
cascaded-from loop. Agitation, airflow,
and pressure (each complete loops with their own probes and actuators)
commonly receive the cascade from DO, altering their respective setpoints to
correct errors in DO.
When more than one loop is configured as the recipient of a cascaded output, they
may respond simultaneously or in sequence, depending on how the cascade has
been set up. Sequential cascades generally give more predictable control
responses. Sometimes a small region of overlap, where two loop setpoints vary
simultaneously, is used to smooth the transition from one loop to another.
21.1 Creating a Cascade
To create a Cascade:
1. From the
GAUGE SCREEN
, press the
CASC BUTTON
. The
CASCADE
CONTROL SCREEN
will appear.