Flourescent and static

[Dave Plowman (News)]

Does a low voltage fluorescent - specifically the small type you might find in a caravan run from 12v where both end pins are paralleled - generate static electricity?

[Andrew Gabriel]

No.

It might be started with a high voltage pulse, but that's not static.

[Dave Plowman (News)]

Right. I've had a stereo PPM (rather like an analogue volt meter) in to look at (they have concentric needles) which are sort of stuck together apparently by static. Only odd thing about it is a small florry lighting it rather than the more usual low voltage miniature tungsten strip lamps.

If you feed one side only, they separate. But soon 'glue' themselves together again when dealing with a usual stereo signal where the two sides are only a few dB apart.

It's a bit of a fiddle to dismantle it so was hoping for a clue before starting. ;-)

[The Nomad]

Magnetised?

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[Harry Bloomfield]

Dave Plowman (News) submitted this idea :

That sounds a bit confused...

They don't work on static, or generate static. The 12v ones use an inverter changing the 12v DC to a higher voltage, sufficient to strike the tube, then maintain it lit.

The heater element is not used as an heater, they are only used as the electrode. The high voltage AC, tends to have a bias towards a switched DC, which causes one end of the tube to blacken. Turning the tube end for end occasionally cures that.

240v versions either use a starter and choke or a similar to the 12v - inverter, often called an electronic ballast.

[Dave Plowman (News)]

The needles appear to be made from aluminium.

[The Nomad]

Ah! OK, not that, then :-)

...

Gungite?

Fluff?

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[Bob Minchin]

I would suspect a small magnetic object to be in between the pole pieces of the meter movements. I've had this with a single moving coil meter but I could imagine something similar interfering with with a dual needle meter.