This is a natural thought and is a good one. It is also a useful idea. Old time vacuumists often had a discharge tube in the line and used a fixed high voltage to gauge vacuum. It was very subjective mind you, but in the hands of an old vacuum head, they knew darned close to the vacuum they were pulling just by the shape, color and character of the discharge.
With a TC gauge on my early demo fusor, I got really good at guessing the pressure based solely on my subjective impressions of the discharge. CertainlyI could easily hit the pressure within 5 microns over the range of 100-5 microns.
For the neophyte,there is no way without a gauge present that any discharge will mean any thing.
Now if we are talking about pressures versus voltage atdischarge beginning, or currents flowing at specific pressures, yes, this will work as a rather accurate gauge, but only after reference points are set for specific geometry systems with a known reference gauge.
Thus, no matter what, some form of reference must be used to calibrate either the eyeball or the electronic gauging system for any specific fusor.
Richard Hull
Created on Thursday, May 10, 2001 11:14 AM EDT by Richard Hull