Date: Tue, 5 Apr 2011 16:04:46 -

Author: Stan Dodds

Subject: Re: Spectral lamp positioning?


Hi Urs,

We have several similar Osram lamps with commercial holders from two
different companies. All are mounted as you say: cylinder axis
vertical, with the metal contacts at the bottom.

Part of the linguistic confusion is with the British site. US usage
would be "vertical, base down", since the connector end of a lamp is
usually called the base. Some ancient vacuum tubes also had an
electrode at the top of the glass envelope, which was called a "cap"
in the US, just to add to the confusion.

I don't know about the different temperatures. They all get pretty
hot, in my experience. If it's operating within voltage/current
specifications and cooled as specified it should be OK.


On Apr 5, 2011, at 3:48 PM, Urs Lauterburg wrote:

> Dear Tap-lers,
> I need some advice:
> A while back I posted a reply to Cliff Bettis's ''Light Bulbs''
> thread that I was looking for a He spectral lamp with a threaded E27
> socket to replace one that broke down as part of a demonstration. In
> fact I could no longer find one with an E27 socket, but after some
> time of searching I was able to locate somebody through this
> collector's forum in Germany who
> supplied me an almost identical lamp but with a P28s socket exactly
> as shown here:
> Note that the data sheet above says under ''burning position''
> ''Vertical cap down''. Additionally I was also lucky enough to find
> a few new P28s bulb holders for this lamp in Germany as well.
> Actually this He lamp will replace one that is mounted inside a
> column along with a Na and a Ne lamp of the same type. The column is
> essentially a long metal tube with three slit shaped openings and it
> stands upright on a base. The three spectral tubes are mounted right
> behind the slits and turned on all at once. At the bottom of the
> assembly there is an incandescent bulb with just a single filament
> of the same length as the slits. We would hand out diffraction
> gratings to the students in the auditorium so they can observe and
> compare the three spectra produced by the three kinds of discharge
> lamps along with the rainbow like continuous spectrum of the
> incandescent filament.
> Now I want to make sure that I am doing this right. On the data
> sheet as shown in the first link of this post they refer to the
> socket as the ''cap''. So ''Vertical cap down'' means that the
> burning position is upright with the socket at the bottom right?
> just want to make sure with you native speakers... :-).
> I would be glad if you could confirm my interpretation as correct.
> Furthermore I noticed the the He lamp would get considerably hotter
> than the two others, Na and Ne even if the current is below the
> nominal rate. Would you think this to be normal? Does He emit more
> in the infrared than the other sources?
> Regards to all you physics demonstrators in the new world
> Urs
> Urs Lauterburg
> Physics demonstrator
> Physikalisches Institut
> University of Bern
> Switzerland