Re: [foxboro] DTIME block

  • From: Rguercio@xxxxxxx
  • To: foxboro@xxxxxxxxxxxxx
  • Date: Thu, 14 Feb 2013 14:53:06 -0500 (EST)

Tried all kinds of variations - 2 buckets, 1 bucket, DTOPT on/off, FOLLOW  
on/off (I was OK with averaging the input and passing directly to the 
output,  etc) but it seemed like it either didn't average the inputs, or the 
output would  decay to near zero by the end of the dead time, even if the input 
had good  values coming in.  I finally concluded that the DTIME I was working 
with  had bugs.  Instead I used 4 calc blocks (to provide a generous amount 
 of "smoothing") to generate a running 24 hour average:
 
CALC 1 - 12 samples taken every 5 seconds into a mem swap ladder and  
averaging those for a 1 minute running average updated every 5 seconds
 
CALC 2 - use 10 @ 1 minute outputs from CALC 1 as 10 input samples taken  
once a minute into a mem swap ladder and averaging those for a 10 minute 
running  average updated every minute
 
CALC 3 - use 6 @ 10 minute outputs from CALC 2 as input  samples taken once 
every 10 minutes into a mem swap ladder and  averaging those for a 1 hour 
running average updated every 10 minutes
 
CALC 4 - use 24 @ 1 hour outputs from CALC 3 as  input samples taken once 
every hour into a mem swap ladder and averaging  those for a 24 hour rolling 
average which updates once an hour
 
I could also have done this in 3 or 4 lines in an IND block with  1440 1 
minute grabs or even 86400 1 second samples, updating continuously, but  am 
religious about following Alex's advice to avoid sequence code wherever  
possible.  Maybe this should be the exception.
 
I have done 1 hr, 4 hr, 24 hr and even 30-day rolling averages this  way.  
Not proud of it, but if you use enough blocks, there is a way.
 
Rick Guercio, P.E.
RG Consulting
918 E Desert Shrub  Drive
Washington, UT 84780
713-805-8742 cell  
 
In a message dated 2/14/2013 9:29:46 A.M. Eastern Standard Time,  
Robert.Putman@xxxxxxxxxxxxxxxxx writes:

Not sure  if this is helpful but this is what I found on the DTIME block in 
 BO193AX.

When DTOPT is not set, the incoming measurement samples at  each block 
execution period are
averaged over the shift time period, for  example to avoid loss of signal 
resolution. The average
measurement values  are shifted through the bucket brigade. To avoid rapid 
change of the  output
signal at each shift time, the output undergoes linear interpolation  
between the last two "oldest"
stored values during each block execution  time.

When DTOPT is set, the averaging of incoming measurement samples  is 
disabled and, at each
deadtime block execution, the current measurement  value (MEAS) is directly 
stored into the
"newest" bucket, while the block  output is updated each deadtime block 
execution with the value
from the  "oldest" bucket.

Looks like the averaging is done on the 1st 2 buckets  only.
What is your delay (DT) set to?
Did you try with DTOPT not set and  2 buckets (NUMBKT = 2)?

Bob

-----Original Message-----
From:  foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] 
On Behalf  Of Rguercio@xxxxxxx
Sent: Thursday, February 14, 2013 9:12 AM
To:  foxboro@xxxxxxxxxxxxx
Subject: [foxboro] DTIME block

Has anyone else  had trouble with the DTIME block not functioning as 
advertised?  We are  running V7.1.1 on the Unix side and 8.3 on the mesh  side.

Can't  seem to get the running average out of the block (yes, I know it's 
averaging  the input, but I'd be happy with that - we tested it by simulating 
an   input and can't get that feature to work).  Have tried with FOLLOW on  
and  OFF, DTOPT 0 and 1, BKTS from 1 to 10, varying the DT, etc.   I'm 
thinking  it's buggy (at least for our Rev) and there might be a QF  I'm 
unaware 
of.
Anybody?

Rick Guercio, P.E.
RG Consulting
918  E Desert Shrub  Drive
Washington, UT 84780
713-805-8742   cell


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