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Re: High temperature probes
Posted by: K. Matthies , E-mail: 6320vijayend@axp1.rz.bam-berlin.de, on October 04, 1996 at 21:53:56:In Reply to: Re: High temperature probes posted by : Peter Hammond on October 04, 1996 at 21:51:05:
Dear Mr. Hammond,
I regret very much answering your questions only now, which I do apologise for.
Concerning your question:
LNN is a Piezo-ceramic recently newly developed by the company Ferroperm /Denmark,
based on Lithium niobate.With this ceramic, we presently reach an application temperature of maximum 650 degrees
centigrade. Therefore, the range of applications is a little larger compared to LiNbO3. This is
also valid with respect to sensitivity. Further the pulse shape is improved at high
temperatures.Concerning your second question:
As inside the probes the internal acoustic coupling is accomplished with glass solder which
is to melt prior to operation, those probes may only be applied at temperatures above 350
degrees centigrade.
However, up to the temperature level of approximately 650 degrees centigrade they may
be exposed permanently to the elavated temperature with no damage.Because the probes have in their front only a thin Lambda/2-diaphragm, it makes sense to
heat them up slowly in order to allow for a balanced heat flow. (approx.
10 min./100 degrees centigrade).
Best regards,K. Matthies
: Dear Mr Matthies,
: Thankyou for your reply to my post.: I was aware that Ferroperm were working on LiNbO3 ceramics but I did not
: know they were so near to success.: Your description of slow heating to high temperature is much as I
: expected. Effectively this would tend to limit application to continuous
: monitoring, surely? This is of course a very valuable task, but wouldn't
: it be nice to be able to use the probe fully portably?: Best regards,
: Dr Peter Hammond,
: Cygnus Intruments.: : Dear Mr. Hammond,
: : The LNN piezo ceramic are developed in a project financed by EC research programme. In the same project, we have made further development in the transducer. The report that you find in the workshop is practically the final report.
: : It is true that these transducers are used in applications which requires large inspection time. We also use these transducers for determining wall thickness in Zinc coating plants. We measure the wall thickness by immersion technic in approximately 450 °C hot Zinc.
: : For your requirement, we have developed other type of transducers. As far as the construction of these transducers are concerned, it is similar to the previous one except that these are housed in plastic material. They are suitable only for continuous application up to 200 °C.
: : Since they posses ceramic delay path, it is possible to use these transducers on hot surfaces upto 1000 °C. However, this is possible in time intervals of 10 sec with 50 sec pause.
: : With best regards
: : K. Matthies