I'm designing a device which will use ultrasonic transducers in a way similar to sonars. Is it absolutely necessary to correct for the drift in the resonant frequency due to temperature fluctuations? How much will the performance of my system decrease should I choose not to to this? How would I even get around doing it?
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3\$\begingroup\$ If you're using a single transducer for both transmit and receive, then the shift in resonance will be the same in both modes and it'll cancel out. If you're using a fixed-frequency driver, though, then you'll lose some sensitivity on both TX and RX since you'll be working on the skirt of the transducer's passband instead of on its peak. If its "Q" is high enough, that is. Why don't you tell us more about the transducer(s) (link to a data sheet?) and, in greater detail, (schematic?) what you're trying to do? \$\endgroup\$– EM FieldsCommented Nov 6, 2014 at 20:25
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2 Answers
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First, generally your transducer is usually in close proximity to your receiving unit (or if they are one and the same). Thus, any change in resonance is likely to occur on both elements at the same time, so it won't affect their send/receive performance. Secondly, the speed of sound in air depends on density and thus temperature, so you may want to take this into consideration. Thirdly, all of this depends entirely on the level of accuracy you require. If you environment is not going to be shifting temperature that much, you can probably get by with estimates based on a median temperature for your environment.
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\$\begingroup\$ Thanks. I know that the characteristics would change for the transmitter and the receiver equally. I was just wondering if the efficiency of sonic power to electrical signal conversion would decrease if I fed the transducers at not exactly the resonant frequency. \$\endgroup\$– SanuuuCommented Nov 7, 2014 at 12:32
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1\$\begingroup\$ Well, that's the thing, efficiency in this case is based directly on the mechanical resonant frequency. It depends on what your driver/transducer is in this case, but if it simply operates on a single mechanically tuned resonance, it will experience the same shift as the receiving element, thus their two resonant frequencies match (assuming same reaction to temperature). You would lose efficiency if your transducer operated at a single frequency with no shift (maybe temperature compensated) while your receiving element is free to float around based on temperature. More details would help. \$\endgroup\$ Commented Nov 7, 2014 at 13:57
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A link to your transducers would help. The ultrasonic transducers that I've used had a fairly broad resonance. One with a nominal center frequency of (say) 4 MHz might be 2 MHz wide. So no temperature changes were observed (or expected.) These were used in single pulse mode. (A single sine wave period.) And so needed to be broadband. Else the single pulse would have caused them to ring for a long time.
answered Nov 6, 2014 at 22:50