Centre freqencies and focusing variations

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Centre freqencies and focusing variations
Posted by: Ed Ginzel , E-mail: ginzelea@hookup.net, on September 02, 1996 at 21:51:17:
1. I have worked with a variety of different PVDF and
co-polymer films from three different manufacturers
to produce high frequency, high resolution transducers.
Although the thickness of the material was adequate to
provide a resonance frequency of 100MHz the best we
could get was a centre frequency of 58MHz.
Even this frequency was only possible by using a
customised pulser producing a single cycle sine wave.
Care was taken to ensure optimum backing density using
araldite epoxy and still nothing approaching 100MHz
was possible. What would cause such a significant
drop in frequency?
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.

Follow Ups:

Re: Centre freqencies and focusing variations Splitt 11:00:30 9/05/96 (size: 2020) (0)

Re: Centre freqencies and focusing variations Robert A. Day 20:30:39 9/04/96 (size: 2132) (1)

Re: Centre freqencies and focusing variations Klaus Brebøl 11:36:42 9/06/96 (size: 3258) (0)

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Comments:
: 1. I have worked with a variety of different PVDF and : co-polymer films from three different manufacturers : to produce high frequency, high resolution transducers. : Although the thickness of the material was adequate to : provide a resonance frequency of 100MHz the best we : could get was a centre frequency of 58MHz. : Even this frequency was only possible by using a : customised pulser producing a single cycle sine wave. : Care was taken to ensure optimum backing density using : araldite epoxy and still nothing approaching 100MHz : was possible. What would cause such a significant : drop in frequency? : 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.

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