Set of HFD needles. 3 x Temperature and 1 x Heater Needle.
The measurement needles of the HFD Sap Flow Meter are made of hollow 1.6 mm stainless steel tubing. They can easily be bent, damaged or broken off if basic care is not taken in handling the instrument. The significant length of the needles relative to this very thin diameter demand additional attention to detail when handling or transporting the needles. Once installed in sleeves within the tree the needles very robust.
NOTE: the needles gain much of their structural strength when combined with the sleeves.
ICT provides sleeves with a closed end to prevent sap and resin from filling the sleeve and gluing the needle in place. This also enables the sleeves to be left in place without the HFD needles installed and to be used again at a later time without the sleeves having become blocked by sap & resin.
NOTE : if it is intended to use the sleeves for more than one growing season it may be advisable to allow a small excess of sleeve protruding from the stem surface to allow for tree growth and increment of the stem, otherwise the sleeves will become engulfed and obscured by the tree making reuse difficult. If this technique is employed it is very important to make allowance for this to ensure the specific depths of insertion for the measurement points are known and adjusted using a insulated spacer