); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY 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: [EMAIL PROTECTED] 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 > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > -- 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: [EMAIL PROTECTED] GPS: Lat N52.00002 Lon E4.37157 Alt 46.2m _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.