Do 0-10V proportional valves and dampers require a sourcing or sinking controller?
From Siemens datasheet, under the section "Function / Mechanical Design" at p.3:


  When the actuator is driven by DC 0…10 V control voltage or by a 3-position signal, it
  produces a stroke which is transmitted to the valve stem.


From the same document, under the section "TECHNICAL DATA" at p.7 (Thanks to Bruce Abbott for pointing out):


  Input impedance for DC 0...10 V is > 100kOhm


Looks like it's most likely sourcing method. This might apply to only Siemens, I don't know. Or maybe it's a standardized or a common method for all.