Probes and Samples

Mini VLQ now available

New Mini VLQ needle probe for thermal conductivity meter TK04The new Mini VLQ is a 50 mm long needle probe with a diameter of 2 mm for small samples. It can be used where standard size probes are too large for the available sample dimensions. This includes compressible materials like soil samples which cannot be tested with the already available Mini HLQ for plane surfaces.

Use the Mini VLQ for samples with a minimum diameter of 40 mm and a minimum length of 60 mm. The Mini VLQ has a measuring range of 0.3 to 6 W/mK and an accuracy of ± 5%.

 

New Mini VLQ   ˅

Specification TK04

standard: ASTM D5334-08

meas. range: 0.1 to 10 W/mK

temp. range: -25 to 125°C

accuracy: ± 2%

Application range

Sample materials TK04 is designed for testing solids (like soil samples, rock, plastics, glass, ceramics, construction materials, wood or foodstuffs), powder, fragments, pastes, gels and viscous liquids, and for in-situ tests in the measuring range of 0.1 to 10 W/mK. The instrument covers a temperature range of -25° to 125°C. All probes can be used for wet materials.

Sample shape and size

Samples can be of any size and shape as long they meet the minimum size requirements. The minimum diameter according to ASTM D5334-08 is 40 mm, the minimum length is the probe length plus 20%. The higher the thermal conductivity, the larger is the necessary sample size. For soil samples, the ASTM requires larger sample dimensions. Details can be found in the technical specification of the probes and in the application notes (PDF) Choosing a suitable probe, Sample preparation and Testing thermal conductivity of soil samples.

Probes

TK04 probe types

Different probe types are available for use with TK04 which can be connected to the same instrument. All probes have a rugged design, are protected against moisture and are maintenance-free. Heating device and temperature sensor are embedded in a stainless steel tube. The probes come pre-calibrated, the users are not required to perform calibration tests themselves.

Please see the technical specification for a summary of all available probes including their measuring range, temperature range and accuracy.

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TK04 needle probe (Standard VLQ) The classical needle probe (Standard VLQ) has a measuring range of 0.1 to 10 W/mK, an accuracy of ± 2 % and a temperature range of -25° to 125°C. The needle requires a drill hole of 2 mm in diameter and approx. 75 mm in length. If the sample material is soft enough, the probe can be inserted into the sample without pre-drilling. Optional guiding tubes are available which are embedded into the probe at the desired measuring position.

TK04 probes for plane surfaces (Standard HLQ and Mini HLQ) Probes for plane surfaces are supplied in two sizes: the Standard HLQ and the smaller Mini HLQ. Both sizes can be used in the temperature range of -25° to 70°C. The Standard HLQ requires a plain and smooth surface at least 88 mm in diameter, it has a measuring range of 0.3 to 10 W/mK and an accuracy of ± 2%. For the Standard HLQ we offer a matching sample container for powder, fragments pastes and viscous liquids. The Mini HLQ is intended for small samples from 50 mm in diameter, it has a measuring range of 0.3 to 3 W/mK and an accuracy of ± 5%.

For field tests a large and robust needle probe (Field VLQ) with a length of 300 mm is available. The measuring range is 0.6 to 4 W/mK, the accuracy is ± 5 % and the temperature range is -25° to 50°C. The Field VLQ is used with guiding tubes which are driven into the ground at the measuring position before inserting the probe.

Choosing a suitable probe for your application

For laboratory measurements, with few exceptions all probe types can be used for all sample materials. In most cases you can choose a probe by temperature range (see the technical specification of the probes) and by shape and size of the available sample pieces, or by sample preparation possibilities.

For in-situ tests always the Field VLQ should be used, the smaller laboratory probes are not adequate for this purpose.