Experimental Physics and
Industrial Control System

Iztok Krapec wrote:

Hi all!

I am using the SSCAN record for scanning and EDM's XY graph to show the results. Is there any way to update the graph each time when new value is added to the arrays of scanned values (DnnDA fields)?
I have the EDM 1-10-1v.

LP

Iztok

How often the array is updated is a function of the SSCAN record and when it decides to post the new array ... I think.

I have used the SCAN record with MEDM and have wrestled with the same need. My solution was to do two plots ... "Scan In Progress" and "Scan Results. "Scan In Progress" plots the current values for the detector vs. the current value of the positioners (DnCV vs PnCV) so it updates at each point. "Scan Results" plots the final arrays. With MEDM, you can put these on top of each other and make one visible at a time (which is cool). An advantage of having both visible is that one can see the previous scan results while the new scan is in progress ("Look, this peak moved!").

I don't know the answer to Iztok's question, but I have some relevant
information.  I also use two plot displays, one for a scan in progress
and one for a completed scan.  I don't much like this, but it's the best
I've come up with so far.

Currently, the sscan record posts arrays (PnRA/DnnDA) only once per scan,
when the scan is finished.  (It holds those arrays for the data-storage
client, while acquiring the next scan's data into private memory arrays.)
The only way to see data from a scan in progress is to plot the scalar
"current-value" fields.  For example, you could plot D01CV (detector 01
current value) against R1CV (positioner-readback 1 current value).

The medm displays I use for plotting scan data while a scan is in progress
also monitor the VAL and DATA fields.  When a monitor is received from the
VAL field, medm understands that a new data point has been posted, and it
appends the most recently received values of monitored data fields to local
arrays.  (The VAL field is posted every data point, after all data fields
have been posted, and it's the *only* field that is guaranteed to be posted
every data point.  If you just stuff data into arrays whenever you get
monitors, you could end up with 100 X values, but only 98 Y values, because
the sscan record currently doesn't post a scalar PV unless its value has
changed.)

Also, medm monitors the DATA field to tell when a new scan has started.
When DATA -> 0, medm clears its plot arrays in preparation for a new scan.

I would like to add the option of posting array data periodically while a
scan is in progress, but this hasn't yet made it to the top of the list.

--
Tim Mooney ([email protected]) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab

References:

SSCAN and EDM Iztok Krapec

Re: SSCAN and EDM Ned Arnold

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