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Ultrasonic Transmitter amplifier

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Kevin Gallagher

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:cry:
I am currently developing an ultrsonic measuring tape. I am having one major problem and that it getting distance (ie the reciever picking up the transmitted pulse). At the moment with no amplification on the Transmitter ( ie o/p of 4047 BE oscillator being fed directly into transducer) and a CA304 op amp configuration on the reciever I'm getting a distance of 1.5 - 2 metres. I was hoping for aroung 10 metres. Does anyone out there have any amplifier configurations for an ultrasonic transmitter that works. Or any other ideas/recommendations that would increase distance would be welcome.

I can give email if anyone wants to send me cct diagram.

Thanks for any help
Kevin
 

jem

New Member
There are two things you can do to increase the measurement range: Increase teh Tx, or make the Rx more sensitive. the push-pull drive scheme Sebi presented is one way to actually double the Tx OP. Just make sure that the CMOS driver is powered at 10VDC (giving 20Vpp across the TX transducer). Most ultrasonic Tx transmitters can operate at 20Vpp, and higher.

As for increasing the Rx sensitivity, if you even want to achieve close to the range you are seeking, you will need time variable amplification. Assuming you are using a microcontroller (to measure the round trip delays etc.), you can have switched gains (maybe by switching on gain setting resistors in your receiver OPAMP) which increases the gain as time between Tx burst and Rx echo increases. You do not want tooo much gain initially since the slightest strays can easily trip your echo detector (giving a false reading), but as the distance to the target increases, you need to really crank it up (the gain) in order to receive even the faintest echo.
 
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