[time-nuts] QCM

[Jeroen Bastemeijer]

Dear Ulrich,

You question is not as much off-topic as you might think. It is all 
about frequency stability and resonators ;-)  In the past I used to work 
with SAW-devices and micro-balances. We developed our own sensors and 
electronics. Search for names like Jakoby, Vellekoop, Lubking and my 
name and you will find the info.

We even did research on zero temperature TC SAW devices. The TC was not 
exactly zero but very small compared to the state of the art in those 
days. The zero TC was achieved by choosing a certain cut-angle of the 
quartz. Together with some other mechanisms (TC of other parts) this 
resulted in an almost zero TC behaviour.

For measuring small quantities (small mass) SAW is a very good option 
too. The advantage is that the relative permitivity of the substance 
doesn't influence the measurement. The SAW has a area which can be 
exposed but where no electrical signals are present.

For measuring humidity I would suggest to use porous silicon instead of 
a QCM. A QCM will depend on a chemical reactive layer which will change 
over time and probably will be reactive to other components as well. In 
our experiments we never liked those chemical reactive layers as they 
where never reliable enough. Their characteristics were changing all the 
time....

73 Jeroen PE1RGE

Ulrich Bangert schreef:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+j.bastemeijer=tudelft.nl at febo.com RETRY
>
> Gentlemen,
>
> again my question is a bit OT: Has anyone of you personal experience
> with QCMs (Quarz Crystal Microbalances) and give me a recommendation on 
>
> a) what surface coating is suggested if the aim is to measure small
> amounts of humidity in clean air
>
> b) where such crystals may be supplied from in small quantities
>
> c) or if anyone is aware of a ready to go humidity sensor based on QCM
> technology
>
> Best regards and TIA 
>
> Ulrich Bangert
> www.ulrich-bangert.de
> Ortholzer Weg 1
> 27243 Gross Ippener 
> Germany
>
>
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-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl
GPS: Lat N52.00002 Lon E4.37157 Alt 46.2m