EMMA: Fermi Chopper

[kjwoodsISIS]

As scientist or technician using EMMA, I want a controller & GUI for the Fermi Chopper, so that I can change the settings of the Fermi Chopper.

Acceptance Criteria

1. The GUI must display the current speed, phase & window.
2. I can use the GUI to change the current speed, phase & window settings.
3. I can use a script to query the current speed, phase & window settings.
4. I can use a script to change the current speed, phase & window settings.

Notes

1. The Fermi Chopper on EMMA is controlled via an SKF MB350PC (G3) controller, which uses a Modbus over serial (RS485) communications protocol.
   1. The disk choppers on IMAT are also SKF choppers (G5 models). It might be possible to adapt the IOC created for IMAT for use on EMMA. See Update build manual for GUI #886 and Add new SKF chopper files #1737.
   2. Until recently, LET used to use an SKF MB350PC (G3) controller. The IOC & GUI could be based on the corresponding SECI VI.
2. See EMMA Instrument Details for additional information.

[kjwoodsISIS]

Note from David Keymer:

In principle, a fermi and disc chopper behave in the same way – they’re still spinning lumps of metal
in the end – so they have the same operator parameters (frequency, phase, window, etc) that we
would set remotely.

However, it all depends on how clever the controller is as to how much logic, if any, is required in
the IOC/VI. From memory, the VI for the G3 is very basic (apart from the MODBUS protocol) and
only reads and writes values, leaving the controller to deal with everything else (as it should do of
course). So with any luck, an IOC for a G3 would also only have to have the same basic functionality.

[KathrynBaker]

Notes from the VI:

Assumption: This is the Mirrortron-SKF MB350PC chopper used previously on LET.

There is no logic in the VI other than the interpretation and building of command packets and responses, but this is specific.

Number of Nodes: 108
Cyclomatic complexity: 15
Screen Shot:

The nominal values are read from a file on startup, file is not human readable.
Also on startup there is some initialisation relating to the parking information.
There is a very specific command packet builder and interpreter, this will need to be reproduced.
The status displays are interpreted from a byte array.
When the values are changed they are written to the file that is loaded on startup (autosave should cover this).
There are about 30 commands programmed in the LabVIEW VI that builds the command packet.
May need to be wary of the serial connection along 485, ensuring the pin allocations and expected behaviours.
Including emulator and test suite this may be >5 points.

[kjwoodsISIS]

Check that this is the right VI - ask @davidkeymer

[Tom-Willemsen]

I had a chat with @davidkeymer - Apparently Mike Brind and Paul Chorley are the people most likely to know exactly what this chopper is. I will drop them an email.