This is our last May installation; for the18th during the European Night of the Museums at Orléans, Musée des Beaux-Arts. Ten Philips Hue LED bulbs are driven by the sap velocity of the plant.
Using :
vid on the codeshare entry for the philips hue driver :
http://www.ghielectronics.com/community/codeshare/entry/733
Interesting … can you explain more about the sap velocity sensor?
Thanks
I will provide code and explanations in a few.
TDP (Thermal Dissipation Probe) Sap velocity sensor is not a new technique, it dates from the original research of Granier, in the 80s, at the french national agronomic research center (INRA)
There is a good introduction there :
http://www.ictinternational.com.au/tdp.htm
The sensor itself is sold by the Dynamax company, who, as far I know, got the IP :
http://www.dynamax.com/TDP.htm
But it is not cheap at all, costing more than 700$ (just the probe/needles you’re seing on the photo, with NO measuring equipment at all)
So, at the Laab team, resourceful as we are, we build ourselves with a similar design, based on this extraordinary useful article :
http://www.mdpi.com/1424-8220/12/1/954
which could also be renamed “cheap sap velocity sensors for the broke” 
merci!
Sap flow sensor, new to me, but now that you explain it, it makes sense and I can think of some applications for it, but I wonder what the effect the sensor has, given it heats the sap and what affect that has on its speed (I’m thinking of what we do with heavy oil in terms of heating it to change its viscosity and hence increasing its ‘flow speed’, I wouldn’t expect oil like impact but possibly some impact).
Here is another interesting paper I found on the topic (granted its from 2004)
http://www.clw.csiro.au/publications/technical2004/tr39-04.pdf
And for fun a study from British Columbia Canada using Sap Flow http://www.for.gov.bc.ca/hre/pubs/docs/spittlehouse2002.pdf