02-11-2018, 10:33 PM
I would go for the increase in resistance as the filament heats up.
The resistance wire in them is pretty consistent even across manufacturers so it should increase by a percentage of the cold value that will be much closer than anything else.
It would not be as reliable for very old pre-war valves as some ran much hotter.
The resistance wire in them is pretty consistent even across manufacturers so it should increase by a percentage of the cold value that will be much closer than anything else.
It would not be as reliable for very old pre-war valves as some ran much hotter.
