I think you're right and that would explain why I can't really measure the capacitive component. You're talking about negative resistance, I had not looked at it that way but it sounds very reasonable, the voltage over the tube will decay while the resistance increases so that would indeed be negative.
I do indeed use a pulse with series resistor, I let the voltage drop from say 150V down to say 100V to turn the tube off. Normally, with a capacitive load, the tube's cathode would then immediately drop to -50V. This doesn't happen, it doesn't even go below 0V most likely because the negative resistance wins over the capacitive properties. I think the inductive component is very small. At some frequency it should resonate I would assume but I can't see that in my step response so the inductance must be very very small. Michel On Feb 18, 1:51 am, John Rehwinkel <[email protected]> wrote: > > How does a nixie behave in the first few hundred micro seconds after > > switching off. Is it resistive, capacitive or inductive? I would > > assume it to be capacitive but that is not exactly what I measure. > > That's a really good question, and I'll admit I haven't attempted to measure > it. So, in the grand tradition, I'll take a guess at it. Said guess is that > the plasma stays ionized for a bit before the atoms settle back down to > ground state, so it would have the electrical properties of an ionized > plasma, which would be: negative resistance. This would decay to capacitance > as the gas became nonconductive. there's of course inductance from the > leads, and the capacitance and inductance are distributed (especially in > larger nixies), making a sort of sloppy transmission line with varying > characteristics. Now I want to see if various nixies have resonant > frequencies, and what I'd get back if I hooked a TDR to a really big one. > > > It > > seems more resistive, so I am wondering if this is normal or am I > > doing something wrong? > > I'm curious as to how you're measuring this in the first place. Are you > using pulses with a trailing voltage and a series resistance, or what? > > - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
