First, I think your high vac pump is a drag pump rather than a turbo/drag but I could be wrong.
I have not used the Varian Penning but I use a very old CVC Penning gauge (50s vintage) at home and when I bought the thing it was pretty well crudded up inside. All cold cathode gauges are demountable so you should take it apart and check for fur growing on the inner surfaces and any deposited conductive material on the insulator. Put it together and it should go.
For the 100 mTorr FS capacitance manometer, it should be zeroed at a pressure at or below its resolution. The normal resolution of this type of gauge is four decades below the full scale. If you want to be really safe, make that 5 decades as measured by the ion gauge.
Never turn the span or linearity pots as you will immediately take the gauge out of calibration. Recal has to be done by comparing with a certified transfer standard capacitance manometer at zero, full scale and 20% of full scale.
My neutron tube is now pumped by a Pfeiffer turbo/drag and I'm using a 1 Torr capacitance gauge with the CVC Penning as the high vac gauge. The CVC measures up to 25 mTorr and has an adjustment pot. My procedure is to pump low enough to properly zero the manometer and then bring the system up to 25 mTorr as measured by the manometer and then do an adjustment of the Penning's pot.
Steve
Created on Friday, April 13, 2001 2:33 AM EDT by Steve Hansen