Device and method for determining the concentration of a vapor

A device for determining a partial pressure or concentration of a vapor in a volume (2), the device comprising:

• a sensor element (5) that is able to be oscillated, the sensor element (5) having a temperature that is controllable to a temperature below a condensation temperature of the vapor, and an oscillation frequency that is influenced by a mass accumulation formed by the vapor condensing on a sensor surface (6) of the sensor element (5);
• a thermal transfer element with a thermal transfer surface (9) and a thermal dissipation surface (18) differing from the thermal transfer surface (9), wherein a rear side (7) of the sensor element (5) facing away from the sensor surface (6) abuts against the thermal transfer surface (9) of the thermal transfer element, and wherein the thermal transfer element is formed by a heating element (8);
• and
• a cooling element (11) that is connected to the thermal dissipation surface (18) in a thermally conductive manner, wherein during a cooling operation, heat is extracted from the sensor element (5) through the thermal transfer surface (9), and flows through the heating element (8) to the cooling element (11).