The economic HFM-25 was designed to meet the growing need for steady-state testing of small samples of insulation for true thermal resistance and thermal conductivity.
Designed with simplicity in mind, a sample is positioned between the two heating – cooling plates. Plate contact is controlled manually, with variable pressure applied with the use of standard weights. Thickness is conveniently reported with included digital gauge. Testing on compressible samples is possible with included shims.
Ambient room temperature is automatically detected, users can choose from 5, 10, 15, and 20 °C delta ranges. One heat flux sensor is integrated into each plate and is used to monitor heat flux (Q/A), generated due to the difference in temperature (ΔT) between the top and bottom plate at regular intervals until steady-state heat flux is observed. The composite heat flux is then used to measure thermal resistance (R) and calculate thermal conductivity (λ) according to Fourier’s Law.
0.01 to 0.3 W/m•K
Delta 5°C, 10°C, 15°C and 20°C at ambient temperature
Type of Sensors
Flux Sensors (x2) with surface thermocouples
Minimum Sample Size
50 x 50 x 2 mm
Maximum Sample Size
Maximum Sample (LxW)
*ASTM C518, C1784, ISO 8301, JIS A1412, and EN 12664
* Applies for materials below 0.1 W/mK
The homogeneity of NIST 1450d high-density fibrous glass board was measured with the HFM-25. Designed to test small samples or locations of 25 mm x 25 mm. The open concept sample clamping allows testing of large samples.
The four corners of the board were measured to analyze the homogeneity of sample. The % RSD from location to location was less than 1%, confirming the homogeneity
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