Function Blocks
PID Function Block
276 HC900 Hybrid Control Designer Function Block Reference Guide Revision 11
2/07
Note 1. When ON, the HiLimOvr parameter causes the meaning of TRC and TRV to be redefined for process
startup rate control. In this case, TRC set ON causes the algorithm to calculate a value to override the default output
high limit.
The initial value of the limit override comes from TRV. This value is held until the configured delay time expires.
A delay time of zero means delay indefinitely. In this case, the output high limit will track the value on TRV until
such time that TRC returns to OFF.
When the delay time expires, the output limit will ramp to the default configured value and the configured ramp rate.
When the ramped output limit equals or exceeds the default configured value, the output limit override status is set
OFF and the default value is used. A ramp rate of zero will cause immediate termination of the high output limit
override.
A transition of the TRC input to OFF at any time will terminate the output limit override function and restore the
limit to the default configured value. The TRC input must transition to OFF before the output limit override
function can be started again.
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