Experimental Physics and
Industrial Control System

Eric Norum <[email protected]> · Mon, 21 Mar 2011 17:24:22 -0700

On Mar 21, 2011, at 4:58 PM, [email protected] wrote:

> Hello,
> 
> I am using medm.
> I have a network anylizer that scans/samples frequency ranges.
> I would like to represent the results in X/Y format using medm.
> Y: sample value
> X: frequency
> 200 samples
> 
> I assume I have to generate the X waveform = # samples on frequency range.
> But can medm autoscale on the horizontal axis since range and # of samples can be changed at every scan by operator? 
> (I believe so, but ...)

Yes, but remember that the waveform record does not post monitors on its .NORD field.   Thus it's a good idea to have a dummy longin record that is forward linked from the waveform record and which gets its value from the waveform record .NORD field and then have MEDM monitor the number of samples to display from that longin record.

> 
> I would like to have a 'cursor' that moves on the waveform.
> Has anyone tries this in medm?
> How did you do this?
> (A possible solution could be to use the sample number i and extract the (X[i],Y[i]), 
> 2 subarrays of 1 elements...)

I didn't' do that exactly, but I did a similar thing (vertical bars on display showing a region of interest)  by adding plots with X from a PV associated with a couple of sliders and with Y from the waveform record.  This drew vertical lines with the extents of the waveform display on the same screen.   A hack, but worked pretty well.
-- 
Eric Norum
[email protected]

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System