Hot Disk TPS

The Hot Disk TPS is able to measure solids, liquids, pastes, and powders for thermal conductivity, thermal diffusivity, and specific heat. These properties can be measured on a broad range of samples sizes; samples as small as 2 x 2 mm, to an unlimited maximum size. For liquids, the sample volume can be as small as 3 ml. A unique feature of the Hot Disk TPS – its ability to measure powders of various particle sizes.

Measured results of thermal conductivity, thermal diffusivity, and specific heat are absolute and quantitative, without the requirement of factory, or user calibrations. The Hot Disk transient plane source (TPS) technology was developed by Dr. Silas Gustavsson, from his award-winning research in thermal conductivity measurements, dating back to the 1960’s. The Hot Disk TPS technology has been widely recognized as one of the most accurate testing methods commercially available, having undergone multiple independent published theory investigations. This acceptance has led to more than 1000 systems sold world-wide and more than 1000+ publications and growing across countless testing applications.

An important testing capability of the Hot Disk TPS is the ability to remove the effects of contact resistance, without the need of a contact agent, between the sensor and sample. The early portion of a test represents contact resistance and is non-linear, when compared to the remainder of the test, representing the heat from the sensor as it dissipates into the sample in a linear fashion. The non-linear portion of the test, representing contact resistance, can be removed automatically or manually after the measurement is made. As the contact resistance does not require normalizing with a contact agent, measurements on materials from insulations to conductive metals are possible, without calibration.

The Hot Disk TPS measures thermal conductivity and thermal diffusivity with different intervals of test times (0.1 to 1280 sec) and sensor diameters (1 to 60 mm). Control of test times are critical when using a transient measurement, as it ensures the true thermal conductivity is representative of the sample dimension and is not just a surface measurement, common to methods using only short test times. The penetration depth of the heat from the sensor is based on three sample qualities: dimensions, thermal diffusivity (mm2/s), and test time. As the Hot Disk measures thermal diffusivity, the results are displayed with representative penetration depth, based on the dimensions of the sample. Test times can be manually selected.

Hot Disk TPS sensors can be used in both two-sided and single-sided configurations. Highly accurate lab testing can be performed by surrounding the flat sensor with a sample piece, on either side. If two pieces of a sample are not available, the unique single-sided sensor, first invented by Dr. Silas Gustavsson in 1983*, can be used. There are two versions of the single-sided sensor available; a standard two-sided sensor can be configured for single-sided testing by placing an insulation material of known properties on one side of the sensor, the second option is a permanently configured spring-loaded single-sided sensor, for convenient testing of large, hard to handle samples.
Gustafsson, Karawacki. July 1983. Transient hot-strip probe for measuring thermal properties of insulating solids and liquids. Review of Scientific Instruments, 54(6):744 – 747.