I'm looking at Gas discharge tubes, I see 3 pin and 2 pin, but I don't find any schematic about how to connect them. My basic use is across a resistor at the end of a antenna wire or across a feed line transformer. It seems obvious the two tube is applicable, but how would I use a 3 wire tube. Where does the 3rd pin go?
Mikek
I found 3 pin at surplus at a very cheap price.
I think the 3 pin ones are used in telephone circuits, the middle leg is earthed, and the outer two legs go to the A and B wires of the pair (neither of which is directly grounded in normal use). For balanced circuits and similar.
The 2 pin ones are more obviously one end grounded, one end to the (single) line you are protecting, in an unbalanced circuit.
-- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk
Three pins is for balanced lines etc. ground the middle pin.
for using three as two either parallel the ends or just use one end and middle.
-- When I tried casting out nines I made a hash of it.
Following up on Mike's response. My computer didn't display the text. I used Google groups to see what you said.
So, Is the 3 pin tube basically two-2 pins tubes wired together, using the center connection going to ground?
If Yes, Can I ground the center pin and tie the two outer pins together and possibly get two strikes instead of one. I'm assuming they fault open. Lightning protection on a long wire. I'm hoping to protect a Vactrol an amplifier input. Not confident about protecting the amp input. :-)
Mikek
Great! Thanks, Mikek
Pretty much, yes. I'm not sure if it is two separate gas-filled spaces either side, or one continuous one. The glass ones glow a pretty orange or purple colour when activated, whereas the 3-legged ones I've got are all ceramic (solid) body, so hard to tell internally.
I can't see why not. The voltage trip would remain the same, you might get a bit of redundancy there :)
-- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk
The two gaps will always have slightly different breakdown voltages.
If the outer pins are connected together, only the gap with the lowest breakdown voltage will fire. Once this gap begins to conduct, the negative resistance characteristic of the resulting spark/arc will cause rapid voltage collapse, preventing the other gap from triggering.
That's why I thought I cold get two strikes out of a 3 pin unit. By strikes, I mean lightning that takes out my termination resistor.
Mikek
On Nov 14, 2019, Bert Hickman wrote (in article):
The three-terminal gas tubes have the center electrode grounded and this electrode is a metal screen or at least has some holes in it, so ions from an arc on one side will drift across and cause the other side to break down as well.
Joe Gwinn
r
One tube 3 electrodes. One advantage is that when one side conducts, the ot her is thereby made to conduct to ground as well.
They can fault to anything from blown apart to a pile of char. Electrode me tal can be deposited on the glass, glass can crack etc, all depending how h ard they get hit.
NT
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