Sap Flow Sensor
Sap flow sensors are instruments for the continuous measurement of water uptake by trees. The basic principle was developed by André Granier in 1985. Two needles are inserted into the sap wood, one above the other, whereas only the upper needle is heated with constant power. The resulting temperature difference between the two needles correlates with the amount of water that is flowing around the needles and can be converted with an empirical formula to water flow per cross-sectional area.
- SF-G, Typical Granier sensor with two needles
- SF-L, Improved Granier sensor with four needles and a much higher accuracy