Experimental Physics and
Industrial Control System

The PV needs to connect. If you get the value right away, you’ll receive a null because the PV has not connected and not received the initial value, yet.

Waiting via a delay will often be sufficient, but

a) You should not wait within the script, i.e. on the UI thread, because otherwise you’ll next ask:

    Why does all of CSS freeze while my script is sleeping?

b) Sometimes you need to wait 3 seconds instead of 0.1.

    Better would be to add a listener to the PV which gets notified as values arrive.

A file dialog box is part of the process, so I may be able to have the wait conducted in the background while the user selects a file.

Thank you for the help.