Re: [foxboro] CALC vs. IND question

There is a CP sizing spreadsheet for CP30s available from the GPS
website short of running an actual CP, it is the best tool available for
sizing purposes. Strongly recommended.

Beyond that, I can tell you that each line of HLBL code is roughly
equivalent to the execution of 1 AIN block. The relationship between AIN
blocks and CALC blocks varies, but a CALC block is a single digit
multiple of an AIN even with 50 steps.

An IND block with 50 lines of code would be the equivalent - roughly -
of 50 AIN blocks.

Also, not all mathematical functions found in the CALC block are
available in HLBL.


Is this useful to you?

Regards,
 =

Alex Johnson
Invensys Process Systems
10900 Equity Drive
Houston, TX 77041
713 329 8472 (voice)
713 329 1600 (switchboard)
713 329 1700 (fax)
alex.johnson@xxxxxxxxxxxxxxxx
 =


-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Mike_Adams@xxxxxxxxxxxxx
Sent: Wednesday, March 26, 2008 4:45 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] CALC vs. IND question

Hello list,

I have some existing compounds in 4 I/A nodes that each have about 20
CALC
blocks running at a 2 sec period with pretty good phasing.  These blocks
are running somewhat arcane mathematical calculations with 15 to 25
steps
each but only 2 or 3 real outputs are generated per CALC block.

The CALC steps are not commented at all.  We are running into problems
where it is becoming harder to keep up with what is going on in these
CALCs
and it is very hard to edit them efficiently.  I am interested in
replacing
these CALCs with IND blocks that would do the same work but be much
easier
to troubleshoot, document & edit.

I know that INDs load the system more than CALCs but I'm not sure by
what
degree.  All 4 control processors involved are CP30s.  Two of these CPs
are
lightly loaded but the other 2 are heavily loaded.

If I configured an IND to run at the same period as a CALC and do the
same
calculations, what would a reasonable guesstimate of the increase in
load
be?  I just want to get a rough idea on a 1:1 comparison for starters.

I realize I can probably do the following to ease the load increase
incurred by going to INDs:

- lengthen the period to 5 sec & phase them well
- put 2 or 3 CALC blocks worth of steps into 1 IND
- place strategic WAIT statements in the IND code

Thanks in advance,

Mike Adams
Mitsubishi Polyester Film, LLC
Greer, SC USA
864-879-5231

 =

 =

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