What is a neon lamp doing in electronic circuit?

Re: What part is this ?

There's a part on a board. It's like a small lamp. It has two electrodes in it and has a glass covering. Is it a glass type capacitor? It has a 1Mohm resistance and a 30nF capacitance.

Added after 2 hours 52 minutes:

I found the part. That is a neon lamp. What may be the use of it in an electronic circuit?
https://upload.wikimedia.org/wikipedia/commons/b/b9/Neon_lamp.jpg

What part is this ?

Neon lamps are typically indicator lamps. The were very popular before LEDs. They require high voltage to ionize the neon inside to make them glow. Typically, I think 60 to 90 volts is required.

Since they pass no current until the voltage is sufficient to ionize the neon, they can also be used as voltage clamps to protect other circuits. If the voltage goes too high, the neon lamp energizes and limits the voltage before it can damage other parts.

Also, it may not be a neon lamp, but a spark gap discharge tube. These have closely spaced electrodes and are designed to internally arc over during power surges or lightning strikes.

Re: What part is this ?

The word neon comes from the Greek "neos," meaning "the new gas." Neon gas was discovered by William Ramsey and M. W. Travers in 1898 in London. Neon is a rare gaseous element present in the atmosphere to the extent of 1 part in 65,000 of air. It is obtained by liquefaction of air and separated from the other gases by fractional distillation.

The French engineer, chemist, and inventor Georges Claude (b. Sept. 24, 1870, d. May 23, 1960), was the first person to apply an electrical discharge to a sealed tube of neon gas (circa 1902) to create a lamp. Georges Claude displayed the first neon lamp to the public on December 11, 1910, in Paris.

Georges Claude patented the neon lighting tube on Jan. 19th, 1915 - U.S. Patent 1,125,476.

In 1923, Georges Claude and his French company Claude Neon, introduced neon gas signs to the United States, by selling two to a Packard car dealership in Los Angeles. Earle C. Anthony purchased the two signs reading "Packard" for $24,000.

Neon lighting quickly became a popular fixture in outdoor advertising. Visible even in daylight, people would stop and stare at the first neon signs dubbed "liquid fire."

Re: What part is this ?

If it is a neon lamp, you can use it to make an AF sawtooth-like oscillator. Connect R and C in series and the lamp in parallel with C, and apply power to the RC circuit - over 200V.
I've seen something like this for an old historical RC measurement bridge - before valves oscillators - at about 1kHz.

Re: What part is this ?

Hmm, I think it is for high voltage clamping in this circuit. Practically how's the performance compared to MOVs or transzorbs?

Re: What part is this ?

Hello,

would be much easier, if we would know the said board's purpose (if known at all)...

If the part is cylindrical with axial wires, than it's probably a surge arrestor or switching sparg-gap. This is actually the same device, but for different applications. Together with the said resistor and capacitor, it forms a very simple self oscillating pulse generator, that could be used e. g. to trigger xenon flash lamps when connected to the primary side of a small ignition transformer. I used it recently to support ignition of a microwave plasma.

As a surge arrestor, it has a more precise voltage threshhold and steep characteristics, but is als much slower than a varistor. Additionally, current flow isn't self quenching, excluding important applications as mains supply. It has been widely used to protect equipment connected to overhead telephone lines.

All gas discharge devices have typically regions of negative resistance in charateristics and thus can be used in self oscillating circuits. It needs extra effort to suppress oszillations, e. g. for a voltage stabilizing circuit.

Regards,
Frank