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TP08 thermal properties sensor

Small size non-steady-state probe for thermal conductivity measurement

TP08 is a probe that offers the possibility to perform a practical and fast measurement of the thermal conductivity (or thermal resistivity) of the medium in which it is inserted at a high accuracy level. It works in compliance with the ASTM D5334-14, D5930-97 and IEEE 442-1981 standards. The TP08 is a small version of type TP02, made for situations where the length of the TP02 poses a problem. The standard TP08 probe has proven its suitability for soils, thermal backfill materials, sediments, foodstuff, powders, sludges, paints, glues and various other materials.

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The Non-Steady-State Probe (NSSP) measurement method (also known as transient line source, thermal needle, hot needle, heat pulse- and hot wire technique) has the fundamental advantages that it is fast and absolute while the sample size is not critical. Hukseflux is specialised in NSSP design. Special models have been developed for in-situ field experiments. For permanent installation in soils, a dedicated model, TP01, is available. TP08 has been designed and tested in collaboration with the Applied Physics Group of Wageningen University.
Hukseflux specialises in Non-Steady-State probe design. The primary model of the Hukseflux product range is the TP02. This model offers optimal measurement accuracy by a combination of its design features. For some applications however the requirements regarding the sample size are such that the needle length and diameter of the TP02 are too large. For this category of samples, TP08 has been designed. Having a needle length of 70 mm, with the junction at around 17 mm from the tip, and a diameter of 1.2 mm, samples of around 80 ml can be analysed. (35 mm depth). In some cases samples can even be smaller (consult Hukseflux). In TP08 the reference junction of the thermocouple is located in the base. A high quality measurement with TP08 requires that not only the sample but also the base are at a stable (preferably the same) temperature. Usually this is achieved by clamping the base into the same material (metal) that holds the sample.


Test method ASTM D5334-14 and D5930-97 and IEEE Std 442-1981
Needle length 70 mm
Traceability NPL
Range (λ) 0.1 to 6 W/m.K
Sensitivity (ΔT) Thermocouple K, ANSI MC96.1-1982
Temperature range total sensor -55 to +180 °C including cable
Accuracy (@ 20 °C) ± (3% + 0.02) W/mK
Temperature dependence of the accuracy ± 0.02 %/K (additional)
Measurement cycle duration 200 s (typical)
Power requirements (switched) 3V, 1 Watt (max)
Medium / sample requirements granular materials, powders, slurries, gels, pastes. Some samples require pre-drilling. Sample size: Min 20 mm radius. Min volume 80 ml. Smaller samples: consult Hukseflux. Caution: please consult the product manual for more details.
Protection needle and base IP68
Protection total sensor IP67
  • Container TP08: Because of the relative importance of the thermal equilibrium between base and sample, an optional container can be ordered with TP08.
  • Alternative designs: Hukseflux is specialised in NSSP design. Alternative models, for instance smaller, more robust or temperature resistant have been manufactured on request.
  • Permanent installation in soils: The dedicated model TP01 is specifically designed for long term monitoring. A separate brochure is available.


Suggested use

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