Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Mon, 30 Jul 2007 13:15:14 -0500

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of 
> Christopher Larrieu
> Sent: Monday, July 30, 2007 12:51 PM
> To: [email protected]
> Subject: correlations application
> 
> Hi,
> 
> I've been tasked with developing a new correlation 
> application to replace
> the storied Correlation Plots from the old SLC control system.
> 
> My intent was to develop an eclipse-based java app to accomplish this.
> 
> However, Earnest Williams and Stephanie Allison suggested 
> that I should look
> into sscan and SynApps.
> 
> While these tools do seem feature-rich, they don't provide 
> all of the things
> that we want.  So my questions are
> 
> (1) can they provide the functionality we want?
> (2) do we need the functionality that we think we want?
> 
> The main issues:
> 
> (a) user-extensibility
> We want our physicists and other users easily to define 
> steps, measures, and step functions using tools they are familiar
with, like Matlab.

The sscan record can certainly do that.  It can do conventional linear
scans (start, stop, step), and also table-mode where a table of target
positions is downloaded.  We use IDL to generate tables for EXAFS, where
the step sizes are different in different parts of the scan (pre-edge,
XANES, EXAFS).

> (b) beam synchronous data acquisition
> We need to use our specially developed beam synchronous data 
> acquisition system to acquire pulse-synchronous data.  How can the
sscan 
> record support this?

I think you can do it with a detector trigger, but need more information
to be sure.

> (c) concurrent use
> Can one perform multiple scans concurrently with the sscan 
> record, or must one pre-create multiple instances of the record to
achieve such?

What do you mean by "concurrently".  Really at the same time (then you
need multiple sscan records) or in quick succession (then one sscan
record can be used and the parameters changed from the client).  Note
that sscan records can be nested to generated N-dimensional scans.

> 
> (d) data types
> Can this system retrieve data of types other than simple numbers?

Yes, it can retrieve arrays.  The detector readback fields are doubles,
so it cannot handle strings, for example.

> (e) design philosophy
> Is it a good idea to put this sort of functionality in an 
> IOC?  It seems sort of limiting to me.  Why do it?  Is it a matter of
using 
> the tools at hand, or are there more compelling reasons that I don't
see, 
> being mostly unfamiliar with IOC level applications?

It was designed this way for performance.  If all of the things being
scanned are in that IOC (which they do not have to be) then scans of
hundreds of points per second can be achieved.  This is difficult to do
over the network from a client.

Now that we have soft IOCs, if you don't have strict performance
requirements, then you don't need to put the scans in the real-time
(RTEMS, vxWorks) IOC, but rather run them on a workstation IOC (Linux,
Windows, etc.)

Mark

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System