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Re: Dual vs lens-focused crystal advantages?

Posted by: Gerhard Splitt , E-mail: sp@kk-a-col.mhs.compuserve.com, on September 09, 1996 at 16:30:49:

In Reply to: Dual vs lens-focused crystal advantages? posted by : Gary Truemner on September 08, 1996 at 20:40:36:

Klaus Matthies asked me to reply to this question as he feels not familiar with this
subject.

1. I do not agree to the statement that lens-focused single crystal probes are more
common for applications where near surface resolution is requested. To my
experience, the near surface resolution of direct contact dual probes is much better
than for direct contact single crystal probes. Even when the single crystal probe is
focused there is still a zone of poor resolution after the transmission pulse or after
the interface echo if a delay probe is used.

2. Of course, dual probes can be optimized by choosing the proper crystal material.
For example, by using piezocomposite transducers the signal amplitude and
resolution will be improved significantly. By taking different kinds of piezocomposite
material for transmitter and receiver crystal you can match them to the electrical
impedance of the transmitter and receiver electronics individually.

3. I see no reasons why not to use dual probes for critical tasks of near surface
resolution.

Gerhard Splitt

: The original Dual crystal contact probes used for near surface resolution seem to have been superceded by lens-focused
: single crystal probes.

: Are there new crystal materials which would give Dual crystal probes an advantage over lens-focus probes? i.e. optimized
: transmitter and receiver crystal material.

: Other than assembly cost of Dual probes, are there clear reasons not to use Dual probes instead of lens-focus single crystal
: probes?



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