[time-nuts] QCM

Bernd T-Online BNeubig at t-online.de
Fri Oct 26 00:20:19 EDT 2007

Hi John,

Neon John wrote:
> A somewhat related question.  Can a quartz crystal be used as a pressure (actually
> medium to high vacuum) sensor?  Specifically, over the range of perhaps 1 Torr to
> 1e-6 Torr.  IOW, over about the same range as a thermocouple gauge.
> At first blush it would seem a natural application.  Not knowing what the second
> blush is.... :-)
First of all there would not be much frequency change compared to the 
undesired effects from temperature, aging, and probably hysteresis for a 
one Torr pressure difference, and the scale would not be logarithmic as 
desired by a vacuum meter. In principle such a sensor would work only, 
if you put the crystal into a box, which is sealed at a reference 
pressure, and a mechanical force proportional to the pressure difference 
is suitably applied to the crystal through a membrane.
So such a sensor would be rather complex and would have very low 
sensitivity with a linear scale from 0 Torr to 1 Torr - which is 
probably not what you wanted to consider.



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