Contents of small neon glow lamps

[[email protected]]

Hello all!

I am curious to know how small neon glow lamps (NE-2, etc) are
constructed. Clearly you start with a small glass tube, and fill it
with neon. What pressure? Pure Ne or a mixture? I understand that
some long neon tubes, as used with multi-kV transformers in signs, have
a little mercury in them along with the gas... do little glow lamps have
mercury? Then you need metallic electrodes - is a particular metal
preferred? Finally, I know that electronic vacuum tubes often contain a
"getter" to help get rid of any residual oxygen; is this done for glow
lamps?

For reference, the kind of lamp I am talking about looks like this
http://www.jameco.com/wcsstore/jameco/Products/ProdImag/27351.jpg
and is maybe 1/4" (6 mm) diameter and anywhere from 1/2" to 1" (12
to 25 mm) long.

Thanks!

Matt Roberds

 

[Art]

Highly probable a mixture of Ne and an inert material. Extremely simple in
design, very probable at slightly above nominal atmospheric pressure. Highly
probable no Hg within these items since they depend only on the ionization
point of the Ne to "fire". Amazing, the Ne ionizes at a specific voltage
[+ - a given %], and produces that nice reddish-orange glow. That fact has
been used to produce oscillators based on the ionization voltage of these
devices, also voltage regulation circuitry. Check out the 'How things work'
web site. Should have much more information regarding these items.

 

[Victor Roberts]

Hello all!

I am curious to know how small neon glow lamps (NE-2, etc) are
constructed. Clearly you start with a small glass tube, and fill it
with neon.

Yes or a mixture of neon and argon.

What pressure?

I believe the pressure is about 20 Torr but am not sure. I disagree
that the pressure is over an atmosphere.

Pure Ne or a mixture?

Pure Neon or neon plus argon.

I understand that
some long neon tubes, as used with multi-kV transformers in signs, have
a little mercury in them along with the gas...

This is where this discussion gets really messy. There are "Neon"
lamps and then again there are "neon" lamps. Let me try to explain.

In my opinion, a Neon lamp contains Neon, at least as the active gas.
Your Neon lamp is called a "glow" lamp because the electrodes are
placed so close together that there is no positive column in the lamp
and the light comes from the "cathode glow", which is one of the
regions with high electric filed that exists close to every electrode.
A Neon glow lamp is optimized to produce light from the cathode glow
region of the discharge. Your Neon glow lamp has cold electrodes which
create a higher electric field immediately in front of the cathode
then would be created if you had hot thermionic cathodes and thereby
increase the intensity of the cathode glow.

In long lamps, be they neon or otherwise, most of the light comes from
the positive column, not the cathode glow. In fluorescent lamps, most
of the UV that hit the phosphor comes from the positive column. In
those long thin "neon" lamps used for signs, virtually all the light
you see comes from the positive column of the discharge.

Now, the industry that makes Neon lamps with cold cathodes also make
other cold cathode lamps of similar shape that may not contain any
neon at all - and they call these "neon" lamps - so the terminology
can get confusing.

do little glow lamps have
mercury?

The ones that use phosphor may have some mercury to generate UV. The
most common red-orange Neon glow lamps do not.

Then you need metallic electrodes - is a particular metal
preferred?

Usually Nickel.

Finally, I know that electronic vacuum tubes often contain a
"getter" to help get rid of any residual oxygen; is this done for glow
lamps?

Can be. Usually barium. An Italian company, SAES, makes barium getters
for fluorescent and other types of discharge lamps. Of course, in
fluorescent lamps, the phosphor acts as a great getter.

For reference, the kind of lamp I am talking about looks like this
http://www.jameco.com/wcsstore/jameco/Products/ProdImag/27351.jpg
and is maybe 1/4" (6 mm) diameter and anywhere from 1/2" to 1" (12
to 25 mm) long.

Typical Neon glow lamp.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

 

[Don Klipstein]

Yes or a mixture of neon and argon.


I believe the pressure is about 20 Torr but am not sure. I disagree
that the pressure is over an atmosphere.

I have heard 8 Torr, but do not know for sure myself.

Pure Neon or neon plus argon.

Based on what I see in my diffraction grating along with what I have
heard before, it appears to me that:

"High intensity" neon glow lamps (e.g. C2A/NE-2H, A1C/"mini NE-2H) have
pure neon.

"Standard intensity" neon glow lamps (e.g. A1A/NE-2, A1B/"mini NE-2",
NE-51) have 99.5% neon .5% argon. The glow is dimmer but the lamps strike
and operate at a lower voltage.
Strangely, the "cathode/negative glow" is made more yellowish by the
argon. It appears to me that in this particular glow, argon detracts less
from the brightest yellow spectral line of neon than from other visible
neon lines, and that the argon in this glow produces only infrared.
In a lamp with a "positive column", the 99.5% neon .5% argon mixture
glows usually hot pink to magenta in color, purpler at lower currents, and
again dimmer than pure neon.

This is where this discussion gets really messy. There are "Neon"
lamps and then again there are "neon" lamps. Let me try to explain.

In my opinion, a Neon lamp contains Neon, at least as the active gas.
Your Neon lamp is called a "glow" lamp because the electrodes are
placed so close together that there is no positive column in the lamp
and the light comes from the "cathode glow", which is one of the
regions with high electric filed that exists close to every electrode.
A Neon glow lamp is optimized to produce light from the cathode glow
region of the discharge. Your Neon glow lamp has cold electrodes which
create a higher electric field immediately in front of the cathode
then would be created if you had hot thermionic cathodes and thereby
increase the intensity of the cathode glow.

In long lamps, be they neon or otherwise, most of the light comes from
the positive column, not the cathode glow. In fluorescent lamps, most
of the UV that hit the phosphor comes from the positive column. In
those long thin "neon" lamps used for signs, virtually all the light
you see comes from the positive column of the discharge.

Now, the industry that makes Neon lamps with cold cathodes also make
other cold cathode lamps of similar shape that may not contain any
neon at all - and they call these "neon" lamps - so the terminology
can get confusing.


The ones that use phosphor may have some mercury to generate UV. The
most common red-orange Neon glow lamps do not.

Based on my experience with a diffraction grating, phosphored "neon"
glow lamps - usually have a mixture of neon and xenon, sometimes a
mixture of neon and krypton.
I am referring to the ones around or under an inch long, having closely
spaced electrodes, glowing without a positive column and generally having
both leads on the same end. Otherwise the lamp is a different animal,
typically a miniature cold cathode fluorescent lamp - and every one of
those I ever saw the spectrum of have mercury. They also have an inert
gas or inert gas mixture in addition to the mercury, and I have detected
neon in some of them.

- Don Klipstein ([email protected])

 

[TKM]

I have heard 8 Torr, but do not know for sure myself.
SNIP

"Standard intensity" neon glow lamps (e.g. A1A/NE-2, A1B/"mini NE-2",
NE-51) have 99.5% neon .5% argon. The glow is dimmer but the lamps strike
and operate at a lower voltage.
Strangely, the "cathode/negative glow" is made more yellowish by the
argon. It appears to me that in this particular glow, argon detracts less
from the brightest yellow spectral line of neon than from other visible
neon lines, and that the argon in this glow produces only infrared.
In a lamp with a "positive column", the 99.5% neon .5% argon mixture
glows usually hot pink to magenta in color, purpler at lower currents, and
again dimmer than pure neon.
SNIP

SNIP

Based on my experience with a diffraction grating, phosphored "neon"
glow lamps - usually have a mixture of neon and xenon, sometimes a
mixture of neon and krypton.
I am referring to the ones around or under an inch long, having closely
spaced electrodes, glowing without a positive column and generally having
both leads on the same end. Otherwise the lamp is a different animal,
typically a miniature cold cathode fluorescent lamp - and every one of
those I ever saw the spectrum of have mercury. They also have an inert
gas or inert gas mixture in addition to the mercury, and I have detected
neon in some of them.

- Don Klipstein ([email protected])

The cathode glow mode of operation makes it possible to use a neon glow lamp
(such as the NE-2) as a fairly accurate volt meter. I have one such device
that's about 40 years old. It's just a single-turn potentiometer calibrated
in volts connected in series along with a fixed resistor to one lead of the
glow lamp. Apply power and turn the pot until the lamp just fires and read
the voltage on the scale.

Terry McGowan

 

[[email protected]]

I am curious to know how small neon glow lamps (NE-2, etc) are
constructed.

Thanks for all the replies! Besides the answers I got here, the
Philips book at Mike's site * is the best reference I have found
so far.

Matt Roberds

* http://www.electricstuff.co.uk/oldbooks.html