Hello

We have had a customer usig 32kHz crystal with our designed oscillator which was pierce topology.

What we are told, is that if the metal lid of teh crystal is left floating teh system is very sensitive to Charge accumulation of 2kV using balloon charged by rubbing.

If the metal lid is grounded the problem goes away.

Does anyone know if this phenomenon is expected that the crystal parameters change due to 2kV charge ?

Regards

ic_engr

Hello Wave,

Let me give you a bit more details. The system being body worn, the person wearing it noted that while jogging or running with poly-ester shirt, the time base moved few second in 5mins time span.

In the lab, the way to replicate was using a balloon rubbed and checkd for static chagre of 2kV.

Any ideas, or still hard to believe, eh?

ic_engr

Grounding the casing of the crystal seems to fix the issue, so wonder is groundign the casing a standard practice or leaving it floating.


ic_engr

ic_engr wrote on Feb 4^th, 2013, 10:24am:


Doesn't sound odd to me. The vibrating crystal is converting mechanical resonance into an electric resonance by piezoelectric properties. Since it is made of piezoelectric material, a large voltage can have mechanical effects, which on their turn change the frequency. Over time it can cause damage in the crystal, affecting reliability. So I guess you should do something about it.