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Sap Flow Sensor Installation:

Updated: Nov 11

What you need, why you need it and what you can do to improve your data.


Essentials for installation:

Before you go to your field site, you should make sure you have-

1. Drill with charged battery

2. Drilling Guide

3. Wax

4. Insulation

5. Tape Measure

6. Chisel (to remove bark)


When installing Sap Flow sensors, it is essential to use a good drill with a charged battery. It can be difficult to drill straight and clean holes with a poor drill, bit, or battery. A drilling guide is your best tool for a better installation.


Accurately spacing the needles allows for an important simplification of the sap flow equation. This allows for multiple variables to be dropped, including specific heat of the sapwood. The only way to keep the needle spacing exact is to drill exact pilot holes for the sensor needles, which can be done with use of the drilling guide. If you are having problems keeping the drilling guide secure, attach it to the tree using clear tape or zip ties.


Even under the best conditions, the holes drilled do not always fit the needle exactly. To minimize contact errors and increase chances of a successful removal, the sensor needles should be lubricated before insertion. This is usually done by lightly coating the needles with beeswax or grafting wax.


The heat pulse velocity method (HPV) for measuring sap velocity relies on the movement of heat up and down the tree from the heater. To increase accuracy, decrease the temperature fluctuations due to external factors. This is easily done using reflective insulation, which is available from East 30 Sensors. Wrap the insulation around the installation site, and secure with tape.




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