Thermtest TLS-100

Portable Thermal Conductivity Meter

A portable transient line source meter, the TLS-100 instrument is used to measure thermal conductivity and thermal resistivity, both in the field and in the laboratory. Designed for testing the thermal conductivity of soil, polymers, and other soft materials; as well as testing the thermal conductivity of concrete, rock, stone, or other hard materials. Tests can be performed with the push of a button and results are displayed immediately.

TLS-100 Specification

MaterialsSoil, Rock, Concrete, & Polymers
Measurement CapabilitiesBulk Properties
Thermal Conductivity0.1 to 5 W/m•K
Thermal Resistivity0.2 to 10 m•K/W
Measurement Time3 min. (100 mm) / 5 min. (50 mm)
ReproducibilityTypically better than 2%
AccuracyTypically better than 5%
Temperature Range-40°C to 100°C
Smallest Sample (100 mm)50 mm (diameter or square) x 100 mm
Smallest Sample (50 mm)50 mm (diameter or square) x 50 mm
Largest Sample SizeUnlimited
StandardsASTM D5334-14, & IEEE 442-1981

Method is continually improved; specifications are subject to change without prior notice.
*Requires chilled circulator.

TLS-100 Highlights


Soil Thermal Conductivity Testing

Standard 100 mm Sensor

The TLS-100 comes with the standard 100 mm sensor for testing for the thermal conductivity of soil, soft materials,  and easy to drill materials. The needle sensor is fully inserted into an isothermal sample and a measurement is made with the push of a button. In 180 seconds, results are displayed for thermal conductivity and thermal resistivity. Saved results can also be exported to a computer, via Micro-SD card or USB connection.

Thermal Dryout Curves soil can be prepared by measuring the thermal conductivity of a sample at different moisture contents as the sample dries from saturation. The typical approach involves drying the soil by heating it at an elevated temperature to speed up the drying process. Sample is removed, weighed, and measured for thermal conductivity at different time intervals until the sample is fully dried.

Thermal Conductivity of Concrete Testing:

Optional 50 mm Sensor

The 50 mm sensor was designed for testing thermal conductivity of concrete, rock, and other hard samples. Drilling the required 4 mm diameter x 50 mm hole in rigid samples is easy with the included masonry drill bit. When testing hard samples, a contact grease is used to improve contact between the sensor and sample.


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Customer Review

The TLS -100 instrument from Thermtest that we purchased has been effective and reliable for measuring the thermal conductivity of the samples in our concrete laboratory. Daniel from Thermtest has been extremely helpful right from the beginning when we considered purchasing this instrument until today with his advice and technical support. He answered all the queries that I had about the instrument and the measurement technique even prior to the purchase. All in all, I am very happy that we chose Thermtest and thank them for providing us with their excellent customer service.

— Ruchita Jani, Postgraduate Researcher at TU Dublin

The TLS-100 device is used in our laboratory for the testing of soil samples. The aim of the measurement is to test the soils as backfill material for high voltage power cables. In our measurements we test the soil at different water contents. Compared to devices from other manufacturers, the TLS-100 is a reliable and precise measuring device. A special advantage is the short measuring time and an excellent customer service.

— Dr.-Ing. Steffen Trinks at Pedotec GmbH Berlin