The Guarded Heat Flow Meter (GHFM-01) follows ASTM E1530-19 for testing thermal resistance and thermal conductivity of solids, such as metals, polymers, composites and paste from -20 °C to 310 °C. The Thermtest proprietary testing stack, replaces the traditional pneumatic movement with advanced motor control, which allows automated control of testing sample thickness, force or pressure applied.
The advanced GHFM-01 is a primary measurement of thermal resistance—thermal conductivity for solids, such as metals, polymers, composites and paste. Specifically, the calculation of thermal conductivity from measurement of thermal resistance is the most accurate method of testing the true thermal conductivity of heterogeneous materials. The steady-state measurement of thermal resistance represents the full sample thickness and mature heat transfer properties.
According to the method, the sample is subjected to a steady-state through-thickness temperature gradient. The thermal conductivity of the sample is obtained by measuring the temperature difference across it, and one additional temperature.
The testing stack is made up of a heater – upper plate, with integrated temperature sensor and heat sink—lower plate with integrated temperature sensor on each side of the sample. Additional temperature sensors are placed near the top and bottom surface of the sample.
Once steady-state temperature across the sample is achieved, the Fourier law equation can be applied. The ratio RS (m²•K/W), equal to the thickness of the sample, d (m) to its thermal conductivity, λ (W/m•K), can be obtained from the temperatures measured:
Metals, Polymers, Composites, and Pastes
Type of Sensors
Thermal Conductivity Range
0.1 to 40 W/m•K
40 to 60 min.
± 1 to 2%
Plate Temperature Range*
-20 to 310 °C
Automated up to 7 KPa (55 psi)
50 to 50.8 mm
Up to 25 mm | Thin-films down to 0.1 mm with optional Software
*Chilled circulator included with each system
For rigid materials, the GHFM-01 plates automatically clamp together for optimum sample contact. When testing compressible materials, the desired height, force or pressure (up to 80 kg, 379 kPa – 55 psi) applied may be set in the software and the plate will automatically stop once desired sample height or pressure is achieved.
All conditions of calibration, such as management of reference materials, temperature steps and pressure are fully automated with the GHFM-01 software. Verification of calibration is performed through built in validation routines.
Using the GHFM-01 Software, the user is able to schedule unlimited temperature steps up to 300 °C. Internal red backlight signals testing in progress.
Approximate Time: 40 to 60 mins.
Approximate Time: 1 min.
Demonstrating the performance of the GHFM-01, measurements on Pyrex 7740 were made up to 300 °C and compared to literature values.
Temperature ( °C)
Direct Measured Values
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