This device can measure by sensing the temperature difference resulting between the sides of flat, thermally conductive surface when heat flow (heat energy) passes through it.

As shown in the figure, a thin plate with a thermal conductivity of λ(W/mK or kcal/mh°C) and a thickness of d (m) is placed in contact with a heat radiating surface, a heat flow (W/m2, kcal/m2h) which goes through the thin plate after it reaches equilibrium can be found by the following method:

Q=(λ/d)·ΔT

Where ΔT = Temperature difference between two sides of the thin plate, and λ and d are known values, Q can be found by measuring ΔT .

The heat flow sensor is made of a thin material with a low thermal conductivity, and its differential thermocouple has multiple contacts to improve its overall sensitivity.