Hi Greg

I'm not familiar with the Optima range but if its similar to the VG 
organic instrument, what type of Pirani head does it use? Have you 
checked the reference heater element in the head itself? It's inside a 
glass encapsulated tube they are very fragile sometimes go open circuit.

Regards

John Hill
UCL

Greg Eischeid wrote:
> Hello fellow mass spec users,
> 
> I have an older Fisons Optima with vacuum monitor issues. I cannot turn the Ion
> gauge on because of error, "pirani tripped." Both Pirani 1 and 2 are reading
> 1e-3 and supported by an external transducer reading. The turbos are at speed
> so there is no reason to believe the source vacuum is not low enough. I have
> checked the continuity of the ion gauge, both filaments are OK and not touching
> the collector. Ive been through the schematics of the vacuum monitor and it
> seems all is operating as it is supposed to. Another more qualified technician
> has tested the monitor without finding anything. I cannot get past this "pirani
> tripped" error. Anybody have any similar experiences or knowledge of the inner
> workings of an old Fisons instrument? As always, thanks for your support.
> 
> ~Greg
> 
> --
> Greg Eischeid--Harvard University
> 20 Oxford Street
> Cambridge, MA 02138 USA
> ph:(617)496-8626 fx:(617)496-4387
> 
> 
>