Loopback connections work with reals as well. We often lock alarm trip
points by doing something like HHALIM = :THISBLOCK.HHALIM.90. It's about
the only way to get system-wide parameter security from a single point
(protection classes in the graphics are not generally a solution, IMHO).
However, I don't think SPT is connectable; it is meant to be an operator
adjustment. So you have to go with SPHLIM/SPLLIM or locking RSP and REMSW
or LR.
Corey Clingo
BASF Corp.
"Jones, Charles R. (Chuck)" <Chuck.Jones@xxxxxxxxxxxxxxx>
Sent by: foxboro-bounce@xxxxxxxxxxxxx
12/15/2004 09:05 AM
Please respond to foxboro
To: "'foxboro@xxxxxxxxxxxxx'"
cc:
Subject: Re: [foxboro] Lock Setpoint Value in Controller
There may be better ways, but when I've needed to do this I link the
remote
setpoint, then lock the PIDA into remote mode by connecting the REMSW to
itself, as in:
:PIDABLOCK.REMSW.1
This, by the way, is the way you link a parameter back to itself, then
provide it with a default value ('1' in this case). I don't know if it is
possible to make reflexive connections with anything other than Boolean
values.
In any event, I don't think it is possible to connect the SPT parameter to
anything. You can connect to it and read it, but you can't connect
anything
to it and write to it. That's why I go with the remote setpoint.
Chuck Jones
Refinery Automation Technologist
Tate & Lyle -- Lafayette South Plant
765.477.5324 - Office | 877.536.9219 - Pager
-----Original Message-----
From: Karppi, Dan (SudburySmelter)
[mailto:DKarppi@xxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, December 15, 2004 2:44 PM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: [foxboro] Lock Setpoint Value in Controller
Hello List Members,
I want to lock the value of the setpoint in a PIDA controller so that it
cannot be changed from the faceplate. I recall that in an earlier post it
was suggested that a configured parameter can be linked to itself in the
block configuration to lock its value. I've searched the archives but
cannot find this post. Does anyone remember how to do this?
Thanks in advance,
Dan Karppi CCST
Instrument Technologist
Falconbridge Limited
Falconbridge, ON
Canada
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