This may be overly simplistic, but what about using a filter in an AIN block
or an LLAG block? A low pass filter really isn't mathematically the same as
a rolling average, but for a lot of the applications where the process
engineers thought they needed a rolling average, we've found that it's close
enough. You'd either need to do the math to calculate the filter time or
experiment until you get a satisfactory value. You could set the PERIOD to
obtain the desired sampling time. Valve position (or anything else where
you don't need accuracy to the nth digit) would seem to be a good candidate
for a filtered value.
-----Original Message-----
From: Steve Rigby [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, September 06, 2000 8:01 AM
To: 'Foxboro DCS Mail List' (E-mail)
Subject: Rolling average
Hi all,
What I would like is a way to calculate the average position of a valve over
the last hour, updated say every minute.
and then available as an input for a block. Any ideas?
Thanks in advance.
Steve Rigby
Air Liquide Industrie BV
Merseyweg 10
3197 KG Botlek-Rotterdam
The Netherlands
Tel: +31(0)181-271131
Fax:+31(0)181-271100
Email:
[EMAIL PROTECTED]
[EMAIL PROTECTED]
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