Recovery time is also dependent on the recombination time for the gaseous ions involved not just on the circuit time constants. Recombination times are typically in the order of ten microseconds or so.
?
Bruce
On 13/07/2023 06:41 NZST Bonkers <stevens.kg@...> wrote:
?
?
I'm not sure what you mean there, I think the arc, or the detection event in a GM tube can be considered 'low' resistance.
I'd like to re-establish credentials as to why we're discussing this on LTSpice's forum.?
1) to show interest in spark gaps, arresters, neons, GM tubes -? what simulation models exist, what's missing and might be nice to have or to develop.?
2) how they are used - I can offer some detail on GM tube drivers, real measurements,?
3) maybe a simplified model for the GM tube as a narrow pulse current sink, enough to discharge its [3pF] capacitance by 50-100V? - in a time that I can confirm by measurement?
4) perhaps evaluate the "quench" circuit mentioned above - is it faster than the tube, does it work, is it any benefit??
5) provide a locus for any future enquiries about this sort of thing.?
6) Ideally, find a poor mans Geiger tube that works well enough and doesn't cost ?300
A basic GM tube spec is here:?https://www.jameco.com/Jameco/Products/ProdDS/2210141.pdf
They recommend 10Meg anode resistance, with their 3pF tube capacitance that's an RC of 30us, which is in keeping with the quoted minimum recovery time of 90us (3xRC).?
I'm guessing the volts drop from V_operating [500V] to V_min [325V] minus a bit, so a swing of 200V, 250V, to guarantee the tube quenches.?
The magnitude and duration of the ionisation current is not specified, but its quick compared to 90us, I'll measure it if I can't find a published figure.?
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Re: Warning: Multiple definitions of model ...
Well, who'd have thought... Out of the blue, I received an
invitation to be a beta tester this evening. ?
--
Regards,
Tony
On 12/07/2023 13:34, Tony Casey wrote:
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I
can't really comment on QSPICE as I haven't tried it. It's not
clear how I can. I signed up for access to the beta test, but
heard nothing more. I haven't joined the user group, either. But
I'm not alone there - only 183 people have, so far. Nevertheless,
good luck to them. Having competition is good.
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Is the QuickSpice good for downlaod & use?
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yep. LTspice was my retirement job
On Jul 12, 2023, at 1:38 PM, Richard Andrews via groups.io <richardandrews.ma@...> wrote:
?Wow, locating hydrocarbon's!
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Gap geometry affects the field strength for a given gap width.
With infinite plane parallel electrodes the voltage required to achieve the critical field strength is proportional to the electrode spacing.
Spark gaps with spherical electrodes were used to measure peak voltages by decreasing the spacing until breakdown occurs. The voltage required to achieve breakdown is a non-linear function of the sphere separation.
Bruce
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On 13/07/2023 02:52 NZST Jerry Lee Marcel <jerryleemarcel@...> wrote:
Le 12/07/2023 ¨¤ 16:45, Richard Andrews via groups.io a ¨¦crit?:
As the gap widens, the voltage required to initiate a spark increases
exponentially.
Are you sure of this? I had a notion that ionization appeared at a given
field strength, which is more or less a direct relationship of voltage
divided by gap length.
Check this
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yep. LTspice was my retirement job
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On Jul 12, 2023, at 1:38 PM, Richard Andrews via groups.io <richardandrews.ma@...> wrote:
?Wow, locating hydrocarbon's!
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Re: POSH (Powershell) tool to manage "user approved" LTspice cmp files
hi eewiz
Thanks for the help..
Some user info-
All controlled cmp files have a fixed name of "MYstandard.xxx" where .xxx=.bjt, .dio, etc.
The script is currently hard configured:
1. All user cmp filenames = MYstandard.xxx where xxx=bjt, or dio, etc.
2. Parent symbol folder for all user MYstandard.xxx files = %AppData%\LTspice\lib\cmp
3. Parent symbol folder for all LTspice standard.xxx files = %AppData%\LTspice\lib\cmp (same as item 2 above)
4. When LTspice -sync is run (-u switch), it runs in foreground. The script waits until LTspice is exited.
??? So, click "OK" when prompted, exit LTspice, and the script will continue to completion.
5. When -u switch is specified, first LTspice is synced, and then the script compares the
??? two cmp files and will only replace the corresponding standard.xxx if difference.
Any comments or proposed changes are welcome.
I'll be uploading a test script file tomorrow.
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Wow, locating hydrocarbon's!
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I am thinking now I'll have to use e (elementary charge), calculate the number of atoms for the direct path of the gap, use Paschen's voltage and do some magic with them.
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I've had very good luck modeling a spark gap as a switch in series with 20V drop in each direction.? The test case was a parallel tank circuit(about 10uF capacitance at 2.5KV and 10uH inductance) used to create a short AC pulse to excite eddy currents in rock formation strata in the interest of locating hydrocarbon bearing rock for oil exploration.? The current amplitude ramps down linearly instead of decaying linearly as it would with a series resistance.? The gap also quenches realistically.
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I'm not sure what you mean there, I think the arc, or the detection event in a GM tube can be considered 'low' resistance.
I'd like to re-establish credentials as to why we're discussing this on LTSpice's forum.?
1) to show interest in spark gaps, arresters, neons, GM tubes -? what simulation models exist, what's missing and might be nice to have or to develop.?
2) how they are used - I can offer some detail on GM tube drivers, real measurements,?
3) maybe a simplified model for the GM tube as a narrow pulse current sink, enough to discharge its [3pF] capacitance by 50-100V? - in a time that I can confirm by measurement?
4) perhaps evaluate the "quench" circuit mentioned above - is it faster than the tube, does it work, is it any benefit??
5) provide a locus for any future enquiries about this sort of thing.?
6) Ideally, find a poor mans Geiger tube that works well enough and doesn't cost ?300
A basic GM tube spec is here:?https://www.jameco.com/Jameco/Products/ProdDS/2210141.pdf
They recommend 10Meg anode resistance, with their 3pF tube capacitance that's an RC of 30us, which is in keeping with the quoted minimum recovery time of 90us (3xRC).?
I'm guessing the volts drop from V_operating [500V] to V_min [325V] minus a bit, so a swing of 200V, 250V, to guarantee the tube quenches.?
The magnitude and duration of the ionisation current is not specified, but its quick compared to 90us, I'll measure it if I can't find a published figure.?
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Just a thought, I was thinking the resistance drops non-linearly and what ever the source can supply is the current.
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Re: Filters (Butterworth, Chebychev etc.)
Oh sorry. Uploaded again.
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Re: Filters (Butterworth, Chebychev etc.)
Your zip contains filt.sub and filter.asy, but your model is looking for filter.sub
?
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From: [email protected] < [email protected]> On Behalf Of
Christoph
Sent: Wednesday, July 12, 2023 9:07 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Filters (Butterworth, Chebychev etc.)
?
I uploaded my filter attempt to the file section. Hope all is self contained and it works.
?
Tony wrote, "I didn't have any trouble downloading Filt.zip - must be something in your Firefox setup. ..."
I think the problem is that the LTwiki website uses http: (not secure https:) in many places.? That was a problem for the main LTwiki webpages too.? Currently, for me, the main LTwiki webpage (for information about LTspice) now uses https:, but the branches
for Vlad's and Bordodynov's files still do not.? I don't use Firefox, but I guess Firefox (depending on its settings) might prevent you from downloading anything with an http: URL.? Google Chrome complains mightily, but if you are persistent and ignore all
its warnings about it, you can get it to download from http: URLs.? Bit of a PITA.
Andy
?
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Understood, he's using the neon as a G-M tube, but the common G-M circuit already addresses the issue very simply.? G-M tube capacitance is about 5pF, the neons I've just measured are under 1pF, so the same principles should apply.?
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Re: Filters (Butterworth, Chebychev etc.)
I uploaded my filter attempt to the file section. Hope all is self contained and it works. Anything to correct? ¡ª Christoph
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Tony wrote, "I didn't have any trouble downloading Filt.zip - must be something in your Firefox setup. ..."
I think the problem is that the LTwiki website uses http: (not secure https:) in many places.? That was a problem for the main LTwiki webpages too.? Currently, for me, the main LTwiki webpage (for information about LTspice) now uses https:, but the branches for Vlad's and Bordodynov's files still do not.? I don't use Firefox, but I guess Firefox (depending on its settings) might prevent you from downloading anything with an http: URL.? Google Chrome complains mightily, but if you are persistent and ignore all its warnings about it, you can get it to download from http: URLs.? Bit of a PITA.
Andy
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Bonkers, "It is possible that the high current pulse when the bulb triggers is responsible for some of the chaotic behavior.? In order to remove the effects of the high current spike when the lamp fires, the following quench circuit was constructed:"
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no probs - and yeah, don't know why he's using a couple of transistors, a very high value resistor is all that is used for G-M tubes.?
The high voltage ensures avalanche multiplication, and the low tube capacitance ensures the detection is quickly quenched, minimising recovery time - and its limit on max detection rate.??
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Paschen's Law ({B} * {p} * {d}) / log({A} * {p} * {d}) - log(log(1+(1/1.2)))-{C} has nothing to do with resistance except that I believe you need to know the voltage to find the current.
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Going to this thread and downloading the downloaded file, I was hoping to see the model of the arrester. What I saw had nothing to do with LTspice, except of course the arrester symbol. I am very disappointed. I have not seen a model of the arrester or discharger and apparently there will not be one. This topic is appropriate for another forum. For example on the physics forum.
Bordodynov.
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Tony Casey
Bonkers
Christoph
Bell, Dave