Mercury arc rectifier

[PerdioPal]

"seem to be just the regular florescent tubes without a phosphor" with a special glass to let through the UV, not quite quartz but better than soda glass for transmission (of UV).

[ppppenguin]

"seem to be just the regular florescent tubes without a phosphor" with a special glass to let through the UV, not quite quartz but better than soda glass for transmission (of UV).

As I understand it, there are two types of fluorescents that are designed to let out UV. They all generate plenty, it's just how much gets out. It's possible the gas filling is tweaked on some types to maximise or minimise UVB and UVC.

One type, often called blacklight blue, gives out mainly UVA with a filter to minimise visible light. Often used in clubs etc for visual effect. The other are the germicidal tubes, giving lots of UVC. Presumably these tubes are quartz. Used for sterilisation and EPROM erasure.

[bobhowe]

Hi Jeffery the glass that was used in UV lamps on stage and in the clubs is made from Woods Glass and the common types were 4FT Fluorescent tubes and 80W 125W ES & 3BC Elliptical Light Bulbs these were based on MBFU Discharge Light Bulbs similar to Street Lighting apart from they had a Tungsten Filament in series so they did not require Control Gear . For large venues a 400w GES UV Light bulb were used as well and these required Control Gear 73 Bob

[ppppenguin]

This gives a lot of information on "black light" etc: https://en.wikipedia.org/wiki/Blacklight

It doesn't answer my original question about how much UV escapes from my MAR. Since the bulb is almost certainly made of ordinary soda glass, UVC and UVB should be negligible but I'm pretty sure that some UVA will escape.

I was amazed to learn that somebody attempted to make an audio amplifier using a mercury arc. See "other" section.
https://en.wikipedia.org/wiki/Mercury-arc_valve

[Mike Watterson]

I have a plasma "arc" speaker kit, not built. Certainly an arc in air can work as a loudspeaker.

[ppppenguin]

The "singing arc" phenomenon was a concern for William Duddell: https://en.wikipedia.org/wiki/William_Du...ing_arc%22

Important work on the subject was done by Hertha Ayrton. She was the first prominent female electrical engineer.
https://www.theiet.org/membership/librar...tha-ayrton
https://en.wikipedia.org/wiki/Hertha_Ayrton

I've no idea how much noise the arc in my MAR makes. Drowned out by the hum from the wound components and the cooling fan.

[ppppenguin]

I've done the perspex side panel. I drilled through all the fixing holes and bolted the metal panel to the perspex. I did most of the cutting with a 10tpi hand saw. This only failed when the amount to be cut went below about 1.5mm. Then I used a rasp, followed by coarse and fine abrasive paper. Even the rounded corners were OK that way. Several saw cuts plus rasp etc. Looks OK, especially as you can barely see the edges.

That panel was actually aluminium, but the front panel is steel. Now I need to find more perspex. I've got a big piece, about 4ft square, but I'd rather not cut into that for the 23" x 18" front panel.

[Mike Watterson]

Thanks, Jeffery. A couple of interesting links and Hertha sounds amazing.

Plasma speaker designs ionize ambient air which contains the gases nitrogen and oxygen. In an intense electrical field these gases can produce reactive by-products, and in closed rooms these can reach a hazardous level. The two predominant gases produced are ozone and nitrogen dioxide.

https://en.wikipedia.org/wiki/Plasma_speaker
Perhaps if I assemble the plasma speaker it should only be for short demos.

I've noticed that there is some RFI from fluorescent tubes even with passive choke ballasts. Maybe you can check out the MAR with a pocket AM radio?

[bobhowe]

Hi Jeffery would a Solarmeter Ultraviolet Radiometer that measures UV in the region of 208 to 400NM for Sunbed tubes measure UV from Katie ?