TP02 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 the highest accuracy level. It works in compliance with the ASTM D5334-14, D5930-97 and IEEE 442-1981 standards. The standard TP02 probe has proven suitability in soils, thermal backfill materials, sediments, foodstuff, powders, sludges, paints, glues and various other materials. 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. TP02 has been designed and tested in collaboration with the Applied Physics Group of Wageningen University.

  • Optimal accuracy
  • Temperature sensor in the base
  • High temperature and moisture resistance


Optimal Accuracy: TP02 incorporates 2 thermocouple junctions in the needle producing a voltage output, U, that is proportional to ΔT. The one in the tip is not heated. The main signal is the differential signal between this hot joint at 1/3 of the length and the cold joint at the tip. In this configuration the voltage before starting the measurement is always small, independent of the medium temperature. In designs with only one sensor in the needle, the signal U will appear on top off a larger signal. The two junction design has a superior accuracy when measuring at high and low temperatures. In addition, by having both the cold- and the hot junction in the needle, the sensitivity to temperature changes of the medium is minimised.

Temperature Sensor in The Base: The reference temperature sensor in the base (Pt1000) serves as a “cold junction” measurement for establishing the absolute medium temperature T. This is required by ASTM.

Temperature and Moisture Resistance: All the materials in TP02 are highly temperature resistant. It has a full stainless steel needle and base. TP02 is completely sealed. It has a welded tip. This no-compromise sealing guarantees the long term stability of the sensor. Designs with glued sealing or epoxy housings are less reliable in this respect, particularly when working in moist environments.

Standard cables and connectors: Putting the Pt1000 temperature sensor in the base allows the use of normal copper core cables and connectors for cable extension of TP02.

Data processing: The data obtained with TP02 can be processed in any normal spreadsheet program.

Suggested Use

  • Studies of soils and soft rock
  • Studies of foodstuff, plastics and powders

Areas of Application


GT Series
CRC Series


Test method ASTM D5334-14 and D5930-97 IEEE Std 442-1981
Needle length 150 mm
Traceability NPL
Range (λ) 0.1 to 6 W/m.K
Sensitivity (ΔT) Thermocouple K, ANSI MC96.1-1982
Temperature range (total sensor including cable) -55 to +180 °C
Accuracy (@ 20 °C) ± (3% + 0.02) W/mK
Temperature dependence of the accuracy ± 0.02 %/K (additional)
Heating cycle duration 100 s (typical)
Power requirements (switched) 3V, 1 Watt (max)
Medium / sample requirements granular materials, powders, slurries, gels, pastes. Some samples require predrilling. Sample size: Min 20 mm radius. Smaller samples: consult Hukseflux. Caution: please consult the product manual for more details.
Protection needle and base IP 68
Protection total sensor IP 67
Options • Alternative designs: Hukseflux is specialised in NSSP design. Alternative models, for instance smaller (see model TP08), 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.
• Solutions for measurement and control: See the TP02 manual or inquire at Hukseflux. A program for Campbell Scientific CR10X is available. Turn key systems are offered for sale: see TPSYS.

Frequently asked questions

How do I choose the right instrument for measuring thermal properties?

Hukseflux offers a wide range of products for material characterization and measurement of thermal conductivity.

We can offer assistance in choosing the right instrument. But first, you should ask yourself the following questions:

  • what material should be analyzed?
  • what are the conditions, for instance concerning temperature and pressure?
  • what specimens are available?
  • are there standards for my application?
  • what level of accuracy do I need?

Hukseflux is a leading manufacturer of thermal conductivity measuring systems and sensors. We have prepared a guide which may assist you in choosing the proper instrument for measuring thermal properties of your material, whether it is soil, plastics, paints, composites, pastes and fluids.

Hukseflux is able to offer highest quality products at an acceptable price level. If we cannot offer you an acceptable solution ourselves, we will tell you who can. Please contact us for further assistance.

Where are the sensors (needle, probe, meter) for measuring thermal conductivity?

Hukseflux sells a range of complete measuring systems including sensors and Measurement and Control Units (MCU). We offer systems and needle type thermal properties sensors for use in the field and for use in laboratory environments.

These thermal properties sensors, TP02 and TP08, are also available as separate probes for use with the user’s own electronics, for instance Campbell Scientific CR1000.

Cannot find what you are looking for? Please contact us.

Can I get training or a rental system for the thermal conductivity measuring instrument of my choice?

Expert training for system operators
Although in general the systems can be operated by following manuals and standards, we can provide you with expert training. Training vastly improves the level of service to the third party, the efficiency of working with the equipment and reduces the uncertainty of the end result.

Equipment rental
Unfortunately we have discontinued our rental services for all systems.