Transpiration Sap Flow – Thermal Dissipation Probe

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The Thermal Dissipation Probe (TDP) transpiration sensor measures sap velocity which is converted to volumetric flow rate. TDP is a simple and affordable device originally proposed by Granier. The basic TDP probe has two thermocouple needles inserted in the sapwood, the upper one containing an electric heater. The probe needles measure the temperature difference (dT) between the heated needle and the sapwood ambient temperature below. The dT variable and the maximum dTm at zero flow provide a direct conversion to sap velocity.

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Dynamax

Category: Plant Physiology

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For uniform trees in a closed canopy, only one sensor per tree is needed. For irregular canopies or with mixed species, sap flow varies around the circumference of large trees. Thus multiple probes are recommended in a single tree to make flow calculations accurately. Normally, install two probe sets per tree for trees 3” to 6” (75 to 150 mm) in diameter, and four probe sets per tree for trees 6” to 18” in diameter (>150 mm). Calibration is recommended for new species.

Features
Dual needle, Granier design with Dynamax upgrades
Easily inserted and removed for reuse
Constant heat, thermal dissipation method
Continuous measurement method
No waiting periods, no heat pulses
Stainless steel needles, Teflon coated
Compatible with most dataloggers
Differentially wired T-type thermocouples
Electronics & connectors sealed – weatherproofed
Wires directly to datalogger, 1 differential channel each

Specification: Transpiration Sap Flow – Thermal Dissipation Probe

Specifications

Length Diameter T-Types T/C's Probe Spacing Power Cable Heater Resistance Operating Volts
TDP-10 10 mm 1.2mm 1ea 40 mm .08 to .12 W 10ft/5 Cond 26 Ohms 2 V
TDP-30 30 mm 1.2 mm 1ea 40 mm .15 to .2 W 10ft/5 Cond 50 Ohms 3 V
TDP-50 50 mm 1.65 mm 1 ea 40 mm .32 W 10ft/5 Cond 78 Ohms 5 V
TDP-80 80 mm 1.65 mm 2 ea 40 mm .5 W 10ft/6 Cond 110 Ohms 7.5 V
TDP-100 100 mm 1.65 mm 3 ea 40 mm .44 W 10ft/7 Cond 145 Ohms 8 V