Re: Centre freqencies and focusing variations tell.
: - The cable lengths between the pulser, receiver and
: transducer are too long. Need to get all very close to
: transducer for best performance.
: - The part is curved and is distorting the return.
: An important test of high frequency systems is to
: examine the RF signal obtained for artifacts that would
: indicate impedance mismatches and other problems both in
: the electronics and the transducer. Generally you should
: expect a clean single cycle return.
: : 2. Recently we have had numerous application where
: : contact focused probes are useful. Three varieties
: : have been manufacured by different companies; one uses
: : flat elements and plastic lenses,
: : another uses spherically shaped elements of uniform
: : thickness and the third uses thick flat
: : piezo-elements ground to a spherical shape on one side.
: : What differences on beam shape and frequency content
: : can be expected.
: I would expect the spherical bowl crystals to give the
: best result but I have never worked with the spherical
: on one side type and would really like to hear how you
: find them.
Piezoceramic ground to sperical shape on only one side
seems to the kind of topic that pops up from time to
time. I used to work for the danish company Ferroperm,
and sometimes did we manufacture small quantities for
experiments. There can be manufacturing problems due to
the variation in thickness, as the poling field gets
very high in the thin regions. But nothing that cannot
be solved. To me it seems as a another good idea, that
never took of.
Robert A. Day was interested in some results, which I
cannot offer directly, but I can suggest a reference.
Focusing Ultrasonic Transducer with Broad Bandwith
of the Plano-Concave and Plano-Convex Shapes.
Proceedings of the 4th Symposium on Ultrasonic Electronics,
Tokyo 1983, Japanese Jour. of appl. Phys. Vol. 23
(1984), Suppl.23-1,. pp122-124
According to my memory, more resent papers have been
published in IEEE trans. on sonics and ultrasonics, but
unfortunately do I not have any references.