Calculator displays

From: Philip.Belben_at_powertech.co.uk <(Philip.Belben_at_powertech.co.uk)>
Date: Tue May 12 07:12:51 1998

>>> By your later e-mail, you have that image form some website. Good, as it
>>> would be almost impossible to make a reasonable ascii sketch of it. They
>>> glow blue (what gas is that? argon?) and are viewed through a green filter.
>>
>> Is it a gas discharge or a fluorescent anode? The latter are often green/blue
>
> I think gas discharge, as they have the mesh anode that you referred to
> in another message.

Hmmm. I'm not convinced. IIRC, vacuum fluorescent displays have a hot
wire cathode (thin, hard to spot) at the front, a mesh electrode near
the back (anode?) and targets with greyish paint on them at the back.
These targets usually glow blue-greenish when hit by electrons. But it
is the paint that glows.

Gas discharge has the cathode suspended in the gas, and it is the gas
around it that glows, not the surface of the cathode. I have never seen
a blue one, but I imagine argon is more likely than mercury vapour
(which radiates mostly UV).

Philip.
Received on Tue May 12 1998 - 07:12:51 BST