Application Notes

alleDie Wärmeflussmessplatten sind für Messaufgaben ausgelegt, bei denen die Temperatur 80°C nicht übersteigt und ein längerer Feuchtekontakt vermieden wird. Für Anwendungen, bei denen die relative Luftfeuchtigkeit 80 % übersteigt oder ein direkter Feuchtekontakt gegeben ist, müssen die Sensoren durch zusätzliche Maßnahmen geschützt werden. Der Grund hierfür besteht darin, dass dünne Kunststoffschichten nicht dampfdicht sind.

A sealing can be achieved by aluminum adhesive foil or wrapping into bituminous foils or butyl rubber. When using metal foil with high thermal conductivity air gaps between foil and sensor have to be strictly avoided. The foil must not reach around the edges of the sensor (thermal bridges)!


When measuring on surfaces it has to be ensured that heat exchange between surface and surrounding medium is not delivered only through convection but for the most part by thermal radiation. It is therefore important that emissivity and absorption rate of the sensor and the surface onto which the sensor is installed are identical. Since emissivity of metal foils differs in a considerable extent from the emissivity of most materials an additional coating with adapted emissivity should be made if necessary.
One sided exposure to humidity for a longer period of time without precautions can cause deformation of the sensor because the surface coating swells up. This is an indication that moisture entered the sensor which can cause a change in the calibration value.
For the attachment on non-absorbent surfaces double sided adhesive foil should be use preferably. Solvent- or water- based adhesives (e.g. acrylic adhesive) can be used on absorbent or permeable surfaces. In these cases thermal effects caused by evaporative heat may affect the measurement in the beginning. Although the sensor is already treated with wax in the manufacturing process it is recommended to cover it with an additional layer of a suited adhesive (e.g. liquid wax) to enable a non-destructive removal from different surfaces.

The measuring leads can be connected to the designated connections by soldering without problems. The pretinned connections are located centrically at the rim of the sensor. A low-powered soldering iron (15…30 W) should be used to prevent an unnecessary heating of the soldering joint.

Due to a low source resistance of the sensors the lead resistance of the measuring cable can be ignored if a high-resistive measuring instrument (usually a few MΩ) is used. This way practically any cable cross-sections are applicable. Furthermore interference such as AC hum are of little consequence which is why the usage of shielded cables is generally not necessary.