[Control Loopy]

I have used AC Tech or Lenze as they are known in some parts of the world - units are small and reasonably priced, plus last a good few years - unlike many of the cheaper options.

Double check the connections and options you can get, as some have 0-10v or potentiometer - they are made to a price so pick the one you need, not all models cover all options.

Hope this helps.