Re: [foxboro] Daily Totalizer Question


This is only conjecture, as I have not actually had to do this sort of
thing before (well, not on I/A at least).  But I would probably have a CALC
or CALCA block do something like this:

STEP01  TIM       ;get # secs since midnight
STEP02  OUT M02   ;save for later
STEP03  SUB M01   ;subtract secs value from previous scan
STEP04  BIP xx          ;secs still incrementing, it's not midnight yet
    .
    .   (code to do accumulation goes here)
    .
STEPxx  IN M02          ;save current TIM value for next scan
STEPxy  OUT M01

This will (ok, should :) execute the accumulator code once on the first
block scan after midnight, as long as the block period is >= 1 second.
With a little more code, you can make it execute at any arbitrary time of
day.  Of course if the operator enters the wrong value before midnight and
leaves it, you still have to fix it, but at least he/she gets up until
midnight to correct it.

Corey Clingo
Sr. Engineer
BASF Corp.



|---------+---------------------------->
|         |           Angela Gruber    |
|         |           <aag43220@hotmail|
|         |           .com>            |
|         |           Sent by:         |
|         |           foxboro-bounce@fr|
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|         |           07/16/2002 11:20 |
|         |           AM               |
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  |        Subject: [foxboro] Daily Totalizer Question                          
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Hi list:

This is my first posting so bear with me.

I figured out a simple way to do this temporarily but I am looking for some
thoughts to see if there is something.  BTW - we recently upgraded to
version 6.3

-----

We had/have a need to calculate a month-to-date production number utilizing
weigh tickets from railcars.  Currently, the operator enters in the daily
railcar loading amount before midnight into a AIN block.  Whatever number
is
in the system before midnight is considered to be the final number for the
day.

To get the month-to-date number, I made a simple MATH block that checks to
see if the daily railcar amount (the AIN block pnt value) has changed.  If
it hasn't changed, it does nothing (assumes the number is the previous
amount).  If it has changed (assumes its a new amount for the current day),
it adds it to the current accumulated value and stores the new number for
the next comparison.  I currently have the block set to a period of 8 (60
minutes) to give it the longest time between scans.  I have also edited
mastercron to reset the accumulated value at the beginning of the month
back
to 0.

It seems to be working (I have only been running it for 3 weeks now).  I
think it could be better.  The problem I could run into (but haven't yet)
is
if an operator incorrectly enters in the wrong number before one of the
hourly scans, the MATH calculates (it sees a change), the operator enters
in
the correct number after the scan time.  The block would then recalculate
again, only it would be too high - I don't know of a simple way to get it
to
subtract out the error other than having us DCS-folk manually fix it.

But ideally, I would like for the period to be every 24 hours -this would
minimize the error mentioned above because it wouldn't matter much if data
was entered in prior to the scan.  At the same time, though, I would like
to
keep it as simple as possible.  Perhaps some sort of script that would
toggle the MATH block from MANUAL to AUTO just before midnight, the block
would calculate (put it on a faster period when its configured so it will
scan while in AUTO), then toggle back to MANUAL just after midnight?  Or
maye something totally different?

Your feedback is much appreciated

Angie Gruber
OxyVinyls, La Porte, TX











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