Synergy Controller Technical Manual, Revision H
Page 214
16.2 Cascade (Part) Temperature Control
Cascade is a control method that uses two control loops and two sensors to provide better performance than
can be achieved with a single loop. The outer control loop provides the setpoint for the second inner control
loop. With this method, the product temperature reaches its setpoint more quickly than with single loop
control, while minimizing overshoot.
Single loop control compares the temperature of the discharge air of the conditioning section to a
temperature setpoint, and adjusts the heating / cooling systems accordingly. Note that temperature is the
process variable used in the following discussion of the Cascade Control feature and although temperature is
the most commonly controlled variable in cascade applications, other process variable can be controlled to
advantage with this feature.
In Cascade control the outer loop senses the temperature of the unit-under-test or a remote sense point that
requires control. The inner loop controls the air temperature. An error signal is calculated and then
processed by the PID algorithm for the outer loop. An output power level signal is produced ranging from –
100% to +100%, which is converted linearly to a temperature setpoint using the set point low limit and set
point high limit temperature settings. This temperature setpoint is sent to the inner loop.
The inner loop monitors the discharge air from the conditioning system and compares it to the temperature
set point generated by the outer loop. An error signal is generated and then adjusted by the Heat and Cool
PIDs. An output power level signal ranging from 0 to 100% is produced and sent to the heating and cooling
systems.
Warning: Careful consideration should be paid to the Cascade Control setup since the chamber
air temperature will often go to these the limits. This will always occur if the product sensor isn’t
connected properly. A secondary limit controller set appropriately should always be used to
prevent damage to the chamber and/or to the unit-under-test (product) in the event of controller
or primary sensor failure. Cascade High Limit should be always be set to the maximum
allowable air temperature for the chamber and product.
Summary of Contents for Synergy Compact
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Page 142: ...Synergy Controller Technical Manual Revision H Page 142 TE1708 6 Relay Board Schematic...
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