What is a sonar transducer?
A sonar transducer is the element in the sonar apparatus that
turns the electrical signal into sound, which is mechanical energy,
and then does the opposite for returning signals. A generator of
some kind creates and amplifies the electrical signal, it is
directed to the transducer, which then makes the conversion, and
the pulse is sent out. The transducer then "listens" for returning
energy, and converts anything that comes back into an electrical
signal which is sent to the receiver. Sonar is (briefly) the use of
sound (which is mechanical energy) to "look at stuff" in in water
or other media. An electrical signal is generated by the equipment,
and it is changed into mechanical energy by a special crystal in
the same way a speaker changes electrical energy into sound we
hear. The transducer is a piezoelectric crystal that works
on the principle of the same name. Let's look at a transducer and
see how it works, but first let's see what the underlying physics
says about it. Piezoelectric crystals are crystals that change
shape when we apply a voltage across the crystal. Depending on the
placement of the leads that apply the voltage and the orientation
of the crystal, it will expand or contract to a DC voltage. If we
reverse the polarity of the applied voltage, the crystal will
contract or expand (respectively) in just the opposite way.
Applying an AC voltage causes the crystal to respond in that same
way, and it will vibrate. These vibrations travel through the water
or other media we are applying it to. The sonar transducer is a
crystal mounted in a "holder" or some kind. It has electrical leads
attached. The whole of this is "packaged" appropriately depending
on whether it is going to be mounted on the hull of a vessel or
held in the hand by an operator. A link is provided to a group of
pictures of different types of transducers posted at photobucket.
Surf on over and have a look.