The HFM-100 Heat Flow Meter method is an easy-to-use rapid technique for thermal conductivity measurement and thermal resistance measurement of insulation products, construction materials, packaging, and assemblies. A measurement of thermal conductivity is an indicator of the ability of a material to conduct heat and can be critical for defining energy efficiency and thermal performance in materials. The Thermtest HFM has been designed and engineered to combine the highest accuracy, repeatability, widest temperature range, and industry-leading performance, all at an exceptional value. Follows international standards: ASTM C518, ISO 8301, and EN 12667.



  • Two flux sensors for accurate measurement of thermal conductivity
  • Peltier heating / cooling plates for rapid control of temperature
  • Thickness is measured to an accuracy of 0.1 mm (0.004 in) with the use of four digital optical encoders
  • Front panel operation allows full control of all HFM functions, or use the intuitive HFM Software for basic and additional functions, such as printing and exporting
  • Plate clamping can be automated or set to a user defined thickness — ideal for compressible materials
  • Follows international standards: ASTM C518ISO 8301, and EN 12667



Materials Insulation, Solids, and Textiles
Type of Sensors Flux Sensors (x 2)
Applications General Testing
Direction Through-Thickness
Typical Thermal Conductivity 0.005 to 0.5 W/mK (0.035 to 3.5 BTU/(hr·ft·°F))
Extended TC Thermal Couple Upgrade Up to 2.5 W/mK (17.3 BTU/(hr·ft·°F))
Measurement Time 30 to 60 min
Reproducibility Typically better than 1%
Accuracy Typically better than 3%
Plate Temperature Range* -20 to 70°C (-4 to 158˚F)
Largest Sample Size 300 x 300 x 100 mm (12 x 12 x 4 in)
Standard ASTM C518ISO 8301, and EN 12667

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


Thermal Conductivity Measurement Heat Flow Meter Graph Thermtest

A sample of NIST SRM 1450d was repeatedly tested to confirm the accuracy and repeatability of the heat flow meter method. Prior to each of 20 measurements, the NIST 1450d sample was removed, and then placed back within the HFM-100 chamber. The certified thermal conductivity for the NIST piece at 20˚C (68˚F) is 0.03239 W/mK (0.2246 BTU/(hr·ft·°F)). The average thermal conductivity value received from all 20 tests was 0.0325 W/mK (0.2253 BTU/(hr·ft·°F)). All tests had a repeatability within 0.5%, and an accuracy within 1% of the certified value.


Heat Flow Meter High Thermal Conductivity Graph

With the added High Thermal Conductivity Kit, the HFM-100 is able to accurately, and efficiently measure higher thermal conductivity materials, such as glass and ceramics. For such applications, an external thermocouple kit is used in combination with the sample being tested. Macor, Quartz, and Pyrex were tested in the HFM from 10˚C to 60˚C (50˚F to 140˚F). All measured values are within the stated accuracy of the system, +/- 5%.