Hot Disk TPS

The Hot Disk Transient Plane Source (TPS) is widely used instrument for the accurate measurement of absolute thermal conductivity, thermal diffusivity, and specific heat of solids, liquids, pastes, and powders. This non-destructive method has a thermal conductivity testing range of 0.005 to 1800 W/mK and can be used to measure bulk properties of homogeneous and heterogeneous materials, as well as directional properties for anisotropic materials. This versatility is greatly appreciated by academic and commercial users alike, which has led to more than 1000 publications on a wide variety of applications.

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Featured Capabilities

Specification

Highlights

Sample measurement

Featured Capabilities

Thermal conductivity, thermal diffusivity, & specific heat
Solids, liquids, pastes, & powders
Follows ISO & ASTM Standards
No calibration
No contact agent
Control of penetration depth with variable test times
Two-sided & single-sided sensors
Bulk & directional properties
Proven method with 1000+ publications

The TPS sensor is comprised of a flat, double-spiral of Nickel, encapsulated between layers of dielectric insulation. The sensor is electrically connected to a separated power supply and electrical resistance sensing circuit. An auto-balancing Wheatstone bridge is used to maximize electrical resistance sensitivity at the sensor spiral, which is critical for measuring a wide range of thermal conductivity. During a measurement, a current passes through the spiral and creates an increase in temperature, which is recorded over time. Heat generated, dissipates into the sample at a rate dependent on the thermal transport characteristics of the material.

A unique feature of the Hot Disk TPS, is the ability to remove the effects of contact resistance from a measurement without the use of a contact agent. Contact resistance presents itself as a non-linear region at the start of the calculated results for the transient measurement. This is easily identified and removed, manually or automatically, leaving a linear slope free of contact resistance.

From this slope, high accuracy thermal conductivity (W/mK) and thermal diffusivity (mm2/s) is calculated, without the need of complex calibration. Additional properties including volumetric heat capacity (MJ/m3K) and thermal effusivity (Ws½/m2K) are automatically calculated and displayed.

Hot Disk TPS Specification

STANDARD ISO 22007-2:2015

Models	TPS 3500	TPS 2500 S	TPS 2200	TPS 1500	TPS 500 / TPS 500 S	TPS M1
Solids, Liquids, Pastes, and Powders
Thermal Conductivity & Thermal Diffusivity
Bulk or Average
Through-thickness
Through-plane
Two-sided & Single-sided Sensors
Minimum Sample Size (diameter or square)	2 mm	2 mm	6 mm	13 mm	13 mm / 6 mm	10 mm × 40 mm
Maximum Sample Size¹	Unlimited	Unlimited	Unlimited	Unlimited	Unlimited	Unlimited
Thermal Conductivity Range	0.005 to 1800 W/mK	0.005 to 1000+ W/mK	0.01 to 500 W/mK	0.01 to 20+ W/mK	0.03 to 100 / 200 W/mK	0.03 to 40 W/mK
Temperature Range	-160 to 1000°C	-160 to 1000°C	-160 to 750°C	-160 to 750°C	-160 to 300°C	10 to 40 °C.

¹ Although there is no maximum sample size, there are limits on depths of heat penetration.
This depth of penetration is determined by available test times and thermal diffusivity (mm2/sec) of the material.

Hot Disk TPS Highlights

Versatility

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.

Absolute – Quantitative

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.

No Contact Agent

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.

Penetration Depth

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.

Two-sided & Single-sided

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.

Sample Measurements

Sample Set-Up

When testing in the laboratory, two sample pieces may be clamped on either side of the TPS sensor. If two sample pieces are not available, the TPS single-sided sensor may be used. For compressible materials, a compression stand may be used to record force applied and thickness of the sample.

Approximate Time: 1 minute

TPS Software

Power and test time parameters may be selected manually to maximize penetration depth for measurement of thermal conductivity. Advanced software features are available for automation of multiple tests or control of temperature.

Approximate Time: 2 minutes

Measurement

Once start measurement is selected, the Hot Disk TPS will first auto-balance an internal Wheatstone bridge for maximum sensitivity. A temperature drift log of 40 seconds is then recorded. Once complete, the test automatically begins, and the temperature rise with time raw data is displayed.

Approximate Time: < 2 minutes

Result Calculations

As the Hot Disk TPS method is absolute, the results are calculated from the temperature rise vs. time graph, after a measurement is complete. At this point, the effects of contact resistance at the early portion of the measurement can be removed manually or automatically with the iTPS Plugin. Results can then be exported to Excel or Notepad.

Approximate Time: 1 minute

Testing Modules

Standard

For measurement of bulk or average thermal conductivity (W/mK), thermal diffusivity (mm2/s), and volumetric heat capacity (MJ/m 3K) of homogeneous and heterogeneous solids, liquids, pastes, and powders. Standard measurements can be made with TPS two-sided and TPS single-sided sensors for highest accuracy and maximum flexibility.

Available on: All TPS Models.

Anisotropic

Directional (axial and radial) thermal conductivity and thermal diffusivity for anisotropic materials. This testing module requires the input of volumetric heat capacity; if not known, it can be easily measured with the TPS specific heat testing module. Anisotropic measurements may be made with TPS two-sided and TPS single-sided sensors.

Available on: TPS 3500, TPS 2500 S, TPS 2200, TPS 1500

Slab

Thermal conductivity, thermal diffusivity, and volumetric heat capacity of sheets or slabs. Ideal for thin conductive materials like steel, aluminum, copper, and graphite. Measurements of samples from 0.04 to 10 mm thick, and as high as 1800 W/mK are possible.

Available on: TPS 3500, TPS 2500 S, TPS 2200, TPS 500 S

One-Dimensional

Designed for measuring along the length of elongated materials, like rods or core samples. This module is particularly powerful for testing complex materials, such as heterogeneous or anisotropic materials, which are difficult to test with standard testing techniques. This testing can be done with the standard two-sided or single-sided sensor formats.

Available on: TPS 3500, TPS 2500 S, TPS 1500, TPS 500 S

THIN-FILM

Designed for the measurement of thermal conductivity on free standing thin-films or coatings (> 0.01 mm). The thin-film testing module is most widely used in the measurement of polymer films, however additional testing of coatings is also possible.

Available on: TPS 3500, TPS 2500 S, TPS 2200

SPECIFIC HEAT

In addition to calculated volumetric heat capacity from the measurement of thermal conductivity and thermal diffusivity, the Hot Disk TPS is able to directly measure, with high accuracy, specific heat. With various sizes of specific heat cells available (7 to 300 mm), unique testing of complex structures and heterogeneous materials is possible.

Available on: TPS 3500, TPS 2500 S, TPS 2200, TPS 1500, TPS 500 S

TPS Accessories

Temperature Platform

Affordable, compact, rapid testing
-150°C, -50°C or 5 to 300°C
Size up to: 40 mm diameter x 20 mm
Two channel TPS switch & Gas purge

TPS Switch

Automate multi-sensor testing
Channels: x 2, x 4, or x 8
Can be combined with furnace

Standard TPS Sensors

One sensor for any sample, 20 mm or larger
Two-sided sensor for accurate lab testing
Single-sided, spring-loaded sensor for testing of large samples

Muffle Furnace

Large sample or multiple samples
Size up to: 150 x 150 x 50 mm
750°C in backfilled environment

Tube Furnace

Option 1: 40 x 40 x 13 mm
Option 2: 75 x 75 x 25 mm
1000°C in backfilled environment

Compression Stand + Temperature

For compressible materials
Force gauge: 10 to 100 N
Distance gauge
Room temp or -40 to 200°C

Extended TPS Sensor

Small sensors for samples as small as 2 mm
Large sensors for heterogeneous samples or large particle powders.

Testing Cells

Liquid cell: 3 ml
Powder cell
Paste cell

Fan Furnace

Affordable, versatile, expandable
Up to 4 samples
300°C, 400°C, & 500°C options
Optional gas purge

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Customer Review

“
Ever since the original contact was made, Thermtest were highly responsive to our needs and has taken genuine interest in our projects. Their assistance in selecting an appropriate unit for our diverse range of samples was crucial, and both the in-depth training and the overall support they have continuously provided us with has been of much benefit.
— Viktor Sanderyd, R&D Engineer at Graphmatech AB

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