RE: Waveform Records

["Mark Rivers" <rivers@cars.uchicago.edu>]

David,

Does the PLC use Modbus?  If so, my Modbus software may let you directly
read that array into a waveform record, which medm or edm can directly
display.  You would not need to write any code.

If it is not Modbus then you will probably need to write device support
for the waveform record to read the PLC and put the data in the waveform
array.

Mark


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov
[mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of David Dudley
Sent: Thursday, September 04, 2008 1:32 PM
To: tech-talk@aps.anl.gov
Subject: RE: Waveform Records

Maybe a little background would help.
I've got a PV where they want to watch real-time historical information
over the past 4 hours.

The PLC that acquires that PV stores this information in a FIFO buffer
once every 60 seconds, with time stamp information should I require it
(the PLC actually has a buffer that stores the last 48 hours, which
means I actually have 2880 samples, all available at any time).  The
desire is to 'see' that information in graphical form if possible, or in
a table form if not.

David

>>> "Dalesio, Leo" <dalesio@bnl.gov> 9/4/2008 1:14:45 PM >>>

Some issues ---
1) waveforms are just arrays. You're device support can fill it any way
you like.
2) there is a circular buffer record that already does this either ring
buffer - or successive averaging or keep high or low for each sample.
3) we do not queue the array - so if your client is not getting them
fast enough in monitoring - then you will loose old arrays. You may even
get half of one and half of another. This system needs to be set up
carefully.
4) There is a subarray record for just reading an area of interest.
5) we did not do the meta data correctly - so no indication of the unit
of time between samples within the array.


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov on behalf of David Dudley
Sent: Thu 9/4/2008 2:04 PM
To: tech-talk@aps.anl.gov 
Subject: Waveform Records
 
Need a little 'training' on waveform records....

1. With a waveform record, with each scan of the I/O device, does the
device read in a single sample, or a whole waveform?

2. Can waveforms be setup to operate in a continuous FIFO manner?  In
other words, a sliding window of data items collected over time?

3. Can 'edm' display a waveform record, and if so, how?  If 'edm'
can't
display them, is there a program that can?

David