Adjusting transducer frequency without ceasing fluid flow through a meter

1. A method, comprising:

without ceasing flow of fluid through a flow meter:

transmitting an ultrasonic signal of a first frequency through said fluid;

determining the quality of said ultrasonic signal;

adjusting said first frequency to a second frequency as a result of said quality failing to meet a threshold; and

transmitting another ultrasonic signal of said second frequency through said fluid.

2. The method of claim 1 , wherein adjusting said first frequency to the second frequency comprises replacing a piezoelectric element used to generate the first frequency with a different piezoelectric element used to generate the second frequency.

3. The method of claim 2 , wherein replacing said piezoelectric element with said different piezoelectric element is done without removing a transducer housing from said flow meter, the transducer housing capable of alternately housing the piezoelectric element and said different piezoelectric element.

4. The method of claim 1 , wherein adjusting said first frequency to the second frequency comprises adjusting the drive voltage applied to a piezoelectric element used to generate both said first and second frequencies.

5. The method of claim 4 further comprising:

determining a quality of the ultrasonic signal and determining a quality of said another ultrasonic signal;

comparing said qualities to determine which of the ultrasonic signal and said another ultrasonic signal has a higher quality; and

based on said comparison, transmitting either said ultrasonic signal or said another ultrasonic signal.

6. The method of claim 1 , further comprising using a single, common acoustic matching layer for both the ultrasonic signal and the another ultrasonic signal.

7. The method of claim 6 , wherein said acoustic matching layer comprises a material selected from the group consisting of glass, ceramic, plastic, glass-filled plastic and carbon-fiber-filled plastic.

8. A flow meter, comprising:

a piezoelectric element configured to resonate at different frequencies;

a matching layer adjacent to said element and configured to perform acoustic impedance-matching said different frequencies; and

circuitry configured to determine quality of signals traversing fluid passing through the flow meter;

wherein the element emits a first signal through fluid passing through the flow meter;

wherein, based on a determination by the circuitry that the quality of said first signal fails to meet a threshold, the element emits a different signal in lieu of the first signal, said first signal and the different signal having different frequencies.

9. The flow meter of claim 8 , wherein the element emits said different signal as a result of the varying of a drive voltage applied to the element.

10. The flow meter of claim 8 , wherein said matching layer is used both when the element emits said first signal and when the element emits said different signal.

11. The flow meter of claim 8 , wherein said evaluation comprises the determination of first signal amplitude and first signal timing accuracy as the first signal is passed through said fluid.

12. The flow meter of claim 8 , wherein said matching layer comprises a material selected from the group consisting of glass, ceramic, plastic, glass-filled plastic and carbon-fiber-filled plastic.

13. The flow meter of claim 8 , wherein the first signal comprises multiple frequencies.

14. The flow meter of claim 13 , wherein the element emits the different signal based on an evaluation of the quality of each of the multiple frequencies of the first signal, and the different signal comprises a single one of the multiple frequencies of the first signal.

15. The flow meter of claim 13 , wherein the element emits the different signal based on a determination of which one of the multiple frequencies of a collected sample of the first signal has a higher quality level than the other of the multiple frequencies.