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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 23, 1996 at 16:23:42:

In Reply to: Re: Dual vs lens-focused crystal advantages? posted by : Gary Truemner on September 19, 1996 at 03:13:46:

Thanks for that interesting discussion,

The advantages of using dual crystal probes instead of single
crystal probes are not dominated by a special "new" crystal
material. The best argument for a dual probe is its excellent
near resolution. This is the reason why corrosion thickness
gauges are working with duals.

For example, a standard 5 MHz dual probe can measure down to
1.0 mm wall thickness. To achieve this excellent near
resolution with a single crystal probe a big effort is
necessary to produce a very high damped probe. Therefore, the
costs for this two probe types may be equal at the end.

Indeed, by using piezocomposite material as transducers it is
very easy to build a inexpensive dual probe with good near
resolution. For a single crystal probe with comparable high
resolution the costs may be even higher in that case.

: thanks again,

: One last detail. It would seem that the advantage of different transmitter versus receiver crystal material is not very large, especially, compared to the costly, difficult dual assembly design.

: Are there new crystal material advantages, which would better justify the large added cost of a dual design ? versus a delay line single crystal probe, or dual design with the same crystal material. ..assuming wide coverage is less important.

: Thanks in advance, for the detailed answers...Gary.

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: Thanks for that interesting discussion, : The advantages of using dual crystal probes instead of single : crystal probes are not dominated by a special "new" crystal : material. The best argument for a dual probe is its excellent : near resolution. This is the reason why corrosion thickness : gauges are working with duals. : For example, a standard 5 MHz dual probe can measure down to : 1.0 mm wall thickness. To achieve this excellent near : resolution with a single crystal probe a big effort is : necessary to produce a very high damped probe. Therefore, the : costs for this two probe types may be equal at the end. : Indeed, by using piezocomposite material as transducers it is : very easy to build a inexpensive dual probe with good near : resolution. For a single crystal probe with comparable high : resolution the costs may be even higher in that case. : : : thanks again, : : One last detail. It would seem that the advantage of different transmitter versus receiver crystal material is not very large, especially, compared to the costly, difficult dual assembly design. : : Are there new crystal material advantages, which would better justify the large added cost of a dual design ? versus a delay line single crystal probe, or dual design with the same crystal material. ..assuming wide coverage is less important. : : Thanks in advance, for the detailed answers...Gary.

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