I can run my experiment in demo mode but not for real when I select the level – I get an error message mentioning the licence. What’s wrong? In demo mode (which is available in AVA whether you have purchased a licence or not), you are able to use all of the possible zones (pale grey boxes) in the Apparatus window to add all of the possible devices. This means you can trial the full functionality of AVA. However, to control real devices you must have purchased an AVA licence of the relevant level: To run a stirring hotplate you need level 1 To run a overhead stirrer you need level 2 To run a circulator you need level 3 To run other devices such as pumps, balances or pH meters/sensors you need level 4. You should remove the device(s) that require a higher licence level, purchase the required licence level, or run in demo mode. N.B. A temperature probe can be used by all levels, but only when (in AVA Software) connected directly to the circulator or stirring hotplate, or when added to the temperature probe zone (pale grey box) top left of the Apparatus window. Any temperature probes added using the miscellaneous zone (top right grey box) would require a level 4 licence.