Re: [foxboro] just a tip
- From: "Corey R Clingo" <clingoc@xxxxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 19 May 2004 08:56:02 -0400
This is one of the things I miss from the brand "H" systems I used to work
with. Those had an adjustable LOCUTOFF parameter in the analog in block
that drove the block's output to 0 if the raw input produced an
engineering unit number that was below the LOCUTOFF value. SCI=7 and
friends on I/A just isn't quite the same... :(
But. as usual, there are 47 possible workarounds. I've used the method
Duc described. The "minimal block" solution is probably to tie LAI or
LLAIND of the AIN to the HOLD on the ACCUM (assuming you weren't using the
low or low-low alarms for anything else), and set LAL or LLALIM to the
desired low cutoff value.
Corey Clingo
BASF Corp.
duc.do@xxxxxxxxxxxxxx
Sent by: foxboro-bounce@xxxxxxxxxxxxx
05/19/2004 07:38 AM
Please respond to foxboro
To: foxboro
cc:
Subject: Re: [foxboro] just a tip
>For some reason, the SCI of 7 (low flow cut-off) doesn't work for me,
>even though it's a pretty plain-jane mass meter sending 4-20mA signal
>through an FBM 4.
Minor correction: I'm at work now and can confirm that it's actually SCI
of
10 that we tried to use for low cut-off for this 12800-64000 linear raw
count signal. Nonetheless, SCI of 10 does NOT work either, and the reason
for that is plain to see when one looks at the logic for SCI=10 in
B0193AW:
SCI = 10: Linear 12800 to 64000 raw counts with low cutoff
IF raw_value <= 12800
THEN
converted_value = LSCO1;
ELSE
converted_value = ((raw_value - 12800) * (HSCO1 - LSCO1) /
51200) + LSCO1;
So, there you have it. The low cut-off is ... zero!
Duc
--
Duc M. Do
Dow Corning Corp.
Carrollton Plant
Carrollton, KY, US
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