We present a dew point temperature sensor with the thermal detection of condensed water on a thin membrane, fabricated by silicon micromachining. The membrane (600 × 600 × ∼1 μm 3) is part of a silicon chip and contains a heating element as well as a thermopile for temperature measurement. By dynamically heating the membrane and simultaneously analyzing the transient increase of its temperature it is detected whether condensed water is on the membrane or not. To cool the membrane down, a peltier cooler is used and electronically controlled in a way that the temperature of the membrane is constantly held at a value where condensation of water begins. This temperature is measured and output as dew point temperature. The sensor system works in a wide range of dew point temperatures between 1 K and down to 44 K below air temperature. In experimental investigations it could be proven that the deviation of the measured dew point temperatures compared to reference values is below ±0.2 K in an air temperature range of 22 to 70 • C. At low dew point temperatures of −20 • C (air temperature = 22 • C) the deviation increases to nearly −1 K.

LTCC is used as a substrate for dew point sensor, e.g. multisensing system consisting of detection system for condensation, temperature sensors, stray field sensor for measurement of condensed water mass. All these components as well as through LTCC vias have been integrated in the LTCC substrate. The mentioned through vias enable the separation of corrosive environment from the electric contact system, the cooling element e.g. peltier element and open new application fields for in line measurement of technical and non-technical processes.