csmstr - Omega Engineering

CSPID – PID MODULE PROGRAMMING
CRIMSON USER MANUAL - MODULAR CONTROLLER
As shown above, the setpoint used during auto-tune is the value 75 % above the difference
between the current PV and the setpoint. This allows the oscillations to occur close to
setpoint, while avoiding excessive overshoot. Since the module performs on/off control
during auto-tune, it is important to set a suitable On/Off Hysteresis value prior to invoking
auto-tune.
Customization of the PID set that auto-tune will yield is possible by adjusting the Tune
Response setting. The Tune Response setting can be set to Very Aggressive, Aggressive,
Default, Conservative, or Very Conservative. Further, the Tune Response setting can be
adjusted by writing 0-4 respectively to the Tune Response register.
INVOKING AUTO-TUNE
The auto-tune sequence uses request/acknowledgement handshaking. To invoke auto-tune,
write the ReqTune bit to a 1. The module signifies that auto-tune is running by setting the
AckTune bit high. When auto-tune is complete, the TuneDone bit goes high. The external
logic should be written to turn off the auto-tune request bit when the TuneDone bit goes high.
At this point, the module sets the AckTune bit back to 0.
If for some reason auto-tune fails to complete, the TuneDone and TuneFail bits both go high.
This situation may occur if, for example, an input fault occurs, and will require that auto-tune
be reinitialized.
An auto-tune request cycle looks like the following…
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