The problem with the ACCUM block is that it does not (or at least didn't the
last time I checked) adjust for skipped BPCs.
This makes it subject to inaccuracies which gets us back where we started.
This makes it a judgement call based on the CP load, frequency of overruns,
convenience of the ACCUM block, etc., etc.
The CALC block gets its time from the clock in the CP. I've never checked in
the where the TIM block gets its time, but the rest of the blocks are based
on the assumption that BPC overruns do not occur.
If you can stand a little slop, use the ACCUM block. If you can't tolerate
any error, use a CALC block. I find the ACCUM superior to the TIM block.
Regards,
Alex Johnson
10707 Haddington
Houston, TX 77043
713.722.2859 (office)
713.722.2700 (switchboard)
713.932.0222 (fax)
[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
-----Original Message-----
From: Mark Chatterton [SMTP:[EMAIL PROTECTED]]
Sent: Thursday, February 01, 2001 3:37 PM
To: 'Foxboro DCS Mail List'
Subject: RE: Block Scan Time
I like the ACCUM block with a fixed MEAS of 1.0 and a MTRFAC set so
the output increments in seconds (or minutes, or hours, or etc.). The SET,
CLEAR, and HOLD features are nice too.
Mark Chatterton
General Mills
Minneapolis, MN
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