Detector with ringdown frequency matching

DETAILED DESCRIPTION The present invention is directed to an ultrasonic detector of the type that may be used to determine the level of a liquid within a tank or the magnitude of liquid flow within a conduit and which has a frequency matching capability that automatically adjusts the frequency at which the transducer generates bursts of energy based upon the transducer ringdown frequency.
The ringdown frequency is that frequency at which the conversion of electrical signals to ultrasonic energy is most efficient.
Preferably, the transducer frequency is adjusted so that it substantially matches the ringdown frequency.
The use of the ringdown frequency for transmission also results in increased sensitivity in detecting echo signals.
In accordance with the invention, a detector is provided with a transducer, means coupled to the transducer for detecting the ringdown frequency of the transducer, and means coupled to the transducer for automatically adjusting the frequency at which the transducer generates energy bursts to substantially match the transducer ringdown frequency.
The transmission frequency may be considered to "substantially match" the ringdown frequency when those two frequencies differ by no more than about one percent.
As a result, the frequency at which the transducer generates energy bursts will be optimally tuned, regardless of environmental conditions such as temperature variations and other conditions, such as the age of the transducer.
The ringdown frequency may be detected by generating an average ringdown frequency.
The average ringdown frequency may be determined by transmitting multiple energy bursts from the transducer, and measuring the ringdown frequency corresponding to each burst.
The ringdown frequency corresponding to each burst may be measured with the use of a "frequency gate," which defines a period of time during which the frequency is measured.
The frequency gate may be shifted after the transmission of each energy burst.
These and other features and advantages of the present invention will be apparent to those of ordinary skill in the art in view of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below