GT SERIES GUIDING TUBES FOR THERMAL NEEDLES TP02, TP08 AND TP07 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. None-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 frequest application however is in soils. 1 2 3 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-SteadyState Probes, and is the inventor of this guiding tube technology. APPLICATIONS 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 predrill a hole, insert the guidig 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). Figure 1 Non-Steady-State Probe. The needle (1) is inserted into a guiding tube (2), typically in a solid sample (3). Version 0616 (page 1 of 2) Hukseflux reserve the right to alter specifications without prior notice HUKSEFLUX™ THERMAL SENSORS . WWW.HUKSEFLUX.COM . [email protected]

1 2 3 4 5 ACCURACY CONSIDERATIONS It has been verified that the addition of a guiding tube does not have a significant impact on the measurement accuracy; when inserting a needle into a guiding tube, essentially a larger diameter needle is created. This results in a larger transient time; one has to wait longer before the desired linear behaviour (of temperature versus the logarithm of time) is occurring. This is normal behaviour for thicker needles. In case it is possible, it is recommended to add a small quantity of glycerol into the guiding tube (before inserting the needle) to minimise the...