The EM3 emissometer, produced by the Themacs engineers
There are a number of portable commercial emissometers that can be used in the field. However, their spectral bands cannot be chosen. In addition, those devices can not be used on curved surfaces without a suitable adapter. They generally perform the measurement over a very small portion of the surface to be studied and are therefore not suitable for measurement on heterogeneous surfaces such as bituminous concretes or building materials encountered in construction and civil engineering.
The proposed modulation method uses a movable screen that obscures a source at fixed temperature. Most existing commercial devices are rotating circular screens with only one incidence. It is therefore necessary to produce a hemispherical three-dimensional screen occulting a source which is itself hemispherical. In addition, to measure the incident flux, it is possible to either measure the temperature of the source or to measure the infrared flux emitted by the latter. In summary, it is therefore necessary to have an infrared source brought to a temperature close to the temperature at which it is desired to measure the emissivity, a screen capable of modulating the emissivity and a system for measuring the incident and reflected infrared flux adapted to the incidences to be measured.