GT Series

Guiding Tubes for Thermal Needles TP02, TP07 and TP08

The GT series guiding tubes are accessories for Non-Steady-State Needle probes. They are intended to facititate measurements in hard soils, concrete, cement and bentonite. Also in case of measurements on large quantities of samples one can use several guiding tubes and one single needle.


Non-Steady-State Probes are used to determine the thermal conductivity of the surrounding medium. The method can applied in various substances such as sludges, fluids, foodstuff. The most frequent application however is in soils. A recurring problem is that insertion into hard soils, bentonites and cements is quite difficult. The main problem is that it is quite difficult to insert needles into these hard materials. The use of guiding tubes in many cases can solve this problem; The guiding tube should be inserted into the medium, and the needle can be inserted at a later stage.

Hukseflux is a leading supplier of Non-Steady-State Probes, and is the inventor of this guiding tube technology.

In case of bentonites and cement the guiding tubes are cast into the material and experiments can be carried out later. In case of hard soils, a typical approach is to pre-drill a hole, insert the guiding tube, compact the soil again, and perform a measurement. In case of dryout experiments guiding tubes are inserted into the samples, dryout can then take place at high temperature (the needle is not inserted).

Suggested Use

  • Studies of ocean sediments
  • Studies of small samples
  • Studies of high cost samples (uranium sludge)

Areas of Application

Material characterization / thermal conductivity measurement


Test method

ASTM D 5334-00 and D 5930-9, IEEE Std 442-1981


sets of 5 tubes, including caps


stainless steel

Needle ends


Protection tube with cap



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