Material moisture content plays an important role in the drying of electrical components. For example, transformers need to be dried in a compartment dryer over several hours. At elevated temperatures negative pressure is generated. The adhesive water is released and drawn from the chamber by a fan. Experience has shown that this contains exhaust dust and particles. Our sensors are compact and can therefore be attached to the unit and give information on the actual moisture content. They can also be placed in the exhaust duct to monitor the dryer humidity.