Patent ID: 6324889
Filing Date: 2001-12-04
Classification: B06B,F24C

Abstract:
An ultrasonic sensor for a fumes extractor hood with automatic compensation regarding temperature and ageing drift, said ultrasound sensor possessing a system-specific resonance frequency and comprising a transmitter and a receiver for monitoring rising cooking vapors conveyed to said fumes extractor hood; an electronic monitoring circuit which, at predetermined time intervals during operation of the ultrasound sensor (5), causes a frequency band of the transmission signals to sweep in the region around the resonance frequency f(o) towards both sides thereof, said monitoring circuit measuring the maximum amplitudes of generated reception signals so as to form an average frequency f(q) from the therewith associated frequencies, and utilizes said average frequency f(q) as a resonance frequency f(o) for the sensor until a successively determined change in the average frequency f(q).