This page is not yet finalized (because we're lazy)! We are working on finalizing it. It will be finalized as soon as possible
We are using a commercial transducer with a center frequency of 5 MHz which has an impedance Z defined by:
With our electronic circuit we access to pulse of amplitude given by the VCC (here 20 V):
the rise time is 420 ns. Ideally, we want a pulse with a duration of 100 ns (half the period of the transducer) with an amplitude of -100 V.
When we plug the transducer, the pulse change:
the amplitude of the pulse is now -12.8 V and the rise time is 5.4 us. The impedance of the transducer reduce the amplitude of the pulse and increase the rise time. By knowing the equivalent electronic circuit we could design the electronic circuit to access the desire pulse.
Smart Materials has lend us transducers in order to test them. Their central frequency is 5 MHz and they are focalised at 80 mm. Due to the specific (LEMO) connector, it take times for us to test them. It is done now. First if we send a pulse 15 V high, the tension measure at the terminals of the transducer is still 15 V high :
The measured echo from a metal plate as a relatively high amplitude :
more than 200 mV peak to peak. It is the highest amplitude we have received on all the transducers we have tested.
We have been recycling the following S-VRW77AK piezoelements. Color pairs are as follows: Yellow/DeepBlue, and Red/LightBlue.
After reconnecting the cables, the whole setup was installed in a plastic tube and waterproofed.
Photographie de la sonde S-VRW77AK
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