# How to drive 1MHz Ultrasonic Transducers

I have 2 ultrasonic transducers (see below picture) facing each other with spacing of 10cm (adjustable). I would like to supply 1 MHz sine wave (from function generator) to one transducer (transmitter) and measure signal amplitude on the receiving transducer (using an oscilloscope).

Can someone please advise the circuitry needed to achieve the above test ?

The transducers are rated for 3Vp-p, not sure about the current they consume.

Below is the transducer specification that was provided by the Manufacturer.

• A datasheet of the transducer would help – m.Alin Nov 5 '14 at 12:38
• If you have a function generator, why is circuitry needed? – Leon Heller Nov 5 '14 at 14:09
• Can you please tell me the reference of the transducers? I am interested in them for a student project... – Rmano Feb 16 '16 at 15:32
• @Rmano, you can find many such transducers on alibaba.com or aliexpress.com, have an online chat with the supplier of the product you are interested in and ask for few samples (don't mention its a student project). – user44776 Feb 20 '16 at 23:24
• @Rmano, search for Ultrasonic transducers, check this out – user44776 Mar 1 '16 at 16:36

## 2 Answers

Yes a function generator will be fine. I don't think user44776 will see anything through the air. Try sticking them on opposite ends of a piece of plastic. And put some 'goop' on the ends to get rid of the air gaps between transducer and plastic. (goop might be something like petroleum jelly.)

Let me add that if the plastic or other solid works (you can try a tub of water too.) Then if your function generator has a burst mode send in on period of a sine wave (at ~1MHz) and measure the time of flight.

• why won't you see anything through air? is it related to the high frequency? As far as I know range sensors based on 40kHz acoustic waves can detect the reflections with no problems – Mehdi Mar 15 '16 at 13:50
• @Mehdi, Different transducers.. the short answer is impedance matching. Air vs water or a solid have very different impedances if not matched somewhat you won't get much power transfer. (I've never used the 40 kHz air-transducers.) – George Herold Mar 15 '16 at 14:39

From the specification, the impedance of your transducer at resonance is equivalent to a 100-350 ohm resistor in parallel with a 1300 pf capacitor. The reactance of the capacitor at resonance (1 MHz) is 122 ohms. Most function generators should be able to drive 3 V P-P into this load. The attenuation in air of sound is about 1.6 db per cm so it is 16 dB at 10 cm. The specification does not give the transmitting sensitivity of the transducer, that is the intensity of sound produced per volt of drive. Thus the sound level reaching your receiving transducer cannot be calculated. Your best bet is to perform the experiment and see what level of signal you receive. Most oscilloscopes can detect levels of 1 millivolt or even less. If you can see the signal on the oscilloscope you are done. If you cannot you will need to provide a voltage amplifier that can amplify at 1 MHz. There are many operational amplifiers that could do this.

• Yes a function generator will be fine. I don't think user44776 will see anything through the air. Try sticking them on opposite ends of a piece of plastic. And put some 'goop' on the ends to get rid of the air gaps between transducer and plastic. (goop might be something like petroleum jelly.) – George Herold Nov 5 '14 at 14:12
• @GeorgeHerold, Many thanks. I would like to accept your comment as an answer, so please convert this comment as an answer to my question. – user44776 Nov 14 '14 at 9:31
• @user44776, Did you get this to work? – George Herold Nov 14 '14 at 13:24
• @GeorgeHerold, yes it did. – user44776 Nov 15 '14 at 6:08