Geiger tube symbol



I’m making a schematic for a geiger counter. I’ll use an SBM-20.

What symbol should I use for it? I didn’t find anything in the official libraries.

Many thanks!


I did a quick google image search on geiger muller tube schematic and see a couple options. Either just use some sort of connector symbol. Or you can draw your own G-M tube symbol. The multiple examples seems to indicate to me that a commonly used symbol looks like the cross section of a test tube on it’s side with a line going down the middle but not touching the curved end. I haven’t looked into IPC documents for the suggestion from the “standard” though.

For your foot print, if you are using the tube off-board make sure you choose a high voltage connector (and high voltage wire). 400VDC is not something to casually connect with header pins… :wink:


Thanks for the tips!

I’ll draw my own symbol then. I’ll try to add it to the official kicad symbols repo, do you have any suggestion under which library?


Probably the Sensor library. I don’t think it is worth creating a whole new Sensor_Radiation library for just one part. (But @Rene_Poschl may disagree.)


I added to the valve library, as it’s similar to those.
PR 1492 was just merged with the new symbol :slight_smile:

Thanks for the tips, @SembazuruCDE!!


I don’t know if I agree with the category. It isn’t a vacuum tube (i.e. valve). There is a mixture of gasses inside it, not a vacuum.

But, I’m not in the KiCad Librarian team…


You are right. It’s not a vacuum tube, but it’s a tube :stuck_out_tongue:

I was not sure about the category. A generic “sensor”, “sensor_current” (because the output is a current pulse), “sensor_gas” or “valve”. I ended up choosing “valve” as it’s powered by high voltage.


I would have gone with the generic sensor…
It could be that joel looked over the category, it is quite a busy time atm.


Although a Geiger tube does somewhat resemble a Valve/vacuum tube, KiCad libaries are not built around resemblance, but to function.

It is therefore also definately not a current sensor. It may deliver an ouput current, but it does not sense current.
There may be gas in it, but that does not make it a gas sensor.
It senses radiation.
I thought a bit about “sensors_optical”, there are also flir sensors in there, but this also feels wrong.

So my vote is with herostrat. I’d put it in “sensor” (no suffix).

Edit: SembazuruCDE was the first to suggest the sensor lib (missed that)
That his alert to Rene did not trigger a response probably means it’s too small a thing to put a single sensor in it’s own library.
Most people will find it through the search function anyway.


Thanks for explaining your reasoning. I have no interest in Geiger tubes, and doubt that I will ever encounter one in real life, but knowing the rationale for classifying the things helps me understand the overall organization of the libraries.



That is what I said way up in reply number 4… This device is a sensor for radiation so it should either be in the generic “Sensor” library or by itself in a new library called “Sensor_Radiation”.


I created PR #1502 to move the symbol to the right library. Hope it is accepted and merged soon.

Thank you all for the comments about the libraries! Now a lot of things makes much more sense to me :slight_smile:


The Geiger-Muller tube symbol from IEEE 315 is as follows:

And the class letter to use in a reference designator is from IEEE 315, Clause 22.4 as follows:
–Regards, Larry


I just found this in IEEE 315A:



These wiggly arrows might be a bit too much for kicads drawing options. Straight arrows should suffice.


What exactly this means?


I agree the wiggly lines are a significant challenge to draw with EESchema’s drawing tools. Unfortunately the wiggles have a specific meaning. Straight line arrows are for light. Wiggly line arrows are for radiation (yes, gamma radiation is light, but alpha and beta radiation are particles). Though, in the first example that Larry provided the radiation lines have dots at the start of the line. This might be an acceptable, and easier to draw in EESchema, radiation line.

@9V1MI, I don’t have time to dig through the standards, but I do remember seeing sections explaining what the individual glyphs in a symbol mean. Is the change from the arrows with dots to the wiggly arrows mandated or suggested? In other words, are the arrows with dots just depreciated or are they obsoleted?

Sidebar: I used to work in a University research lab and we maintained several neutron monitor stations. These stations used NM64 tubes, essentially G-M tubes specifically tuned for detecting the collision debris of cosmic neutrons colliding with lead. (Yes, we weren’t using lead as a shielding material, rather as the target material for the particles we were detecting.) As I remember, we had the metal enclosure grounded (for safety), and fed a negative high voltage to the wire down the center. Thus our symbols would have a minus where the plus is in the above symbol examples. I don’t remember the schematics so I don’t know what symbol we actually used though.


KiCad incorrectly calls the class letter a reference designator, whereas a basic reference designator consists of a class letter portion and a number. On a schematic diagram the reference designator of a Geiger counter tube or Geiger-Muller counter tube would be V#, just like for a resistor the ref des would be R#, for a capacitor it would be C#, and for an IC it would be U#. (the # symbol–called an octothorpe) stands for the number.


As to whether the squiggly line is deprecated or obsolete–yes. The straight lines or squiggly lines are defined in IEC 60617 as appear in IEEE 315A as follows:

You should follow the up to date symbols/information.


That is the straight line with the dot is deprecated and obsolete. In other words don’t use it.