Re: [foxboro] Unlinked Input Secured Error

Jeff,
A Controller block which has its LOCSP option configured true, secures the
LR parameter when the block initializes. LOCSW and REMSW overrides have
higher precedence, but LR stays secured when LOCSW and REMSW are no longer
asserted.

check:  LOCSP
Local Setpoint Secure is a Boolean input (normally set to 0). When true,
LOCSP provides lockout of user write access to the LR parameter. If LOCSP is
configured true, the block secures LR in local when it initializes and
maintains LR in the secured state. The LOCSW and REMSW overrides have higher
precedence, but LR remains secured when they are no longer asserted.

If you set LOCSP=1 first, and then try to connect .LR you get this message
in ICC.  Set LOCSP=0, fixes this, as connecting to .LR is sufficient for
your application.  LOCSP is rarely used, as pulsing/sustaining LOCSW/REMSW
is handy as others have mentioned.

Comment on the application:
If you have 0.0 for the low scale (A flow loop for example) you may get not
always get the valve to fully close even with a 0.0 setpoint, depending on
transmitter calibration.  Also a simple switch is rather aggressive.  You
could ramp the setpoint (using additional blocks).  If setpoint response is
important, check the SPLAG tuning setting which adjusts how the controller
responds to setpoint changes. Set SPLAG=1.0 for fast response, or 0.0 to
integrate slowly without the PROPORTIONAL control action. You may also
consider putting the controller to manual and forcing the output to 0.0.
Your scheme would do nothing if for example the controller was already in
MANUAL.  One way to do this is to toggle the HOLIM from 100% to 0% with the
MANCLP = 1 (HOLIM effective in MANUAL), there are other ways such as using a
CALCA block to adjust TRACK, TRKENL, MANSW, & AUTSW.

Best regards,

Rick Rys
www.R2controls.com
1 Cherry Street
Mansfield, MA 02048
508-339-6633 Home Office
508-369-5186 Mobile


 
 
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