Author Topic: Would a neon bulb work in a multi-meter for circuit protection?  (Read 3581 times)

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Offline joseph nicholas

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I've been thinking a neon tube across the input of a DVM might work as a protection circuit instead of a GDT.  They are essentially the same thing.  Any opinions?  I say this because it would give a visual indication that ac is present in the circuit you are testing as well as providing some limited shunting of voltage spikes in DC applications.  It seems it really is just a GDT, but of course, not rated.  Just thinking out side the box.
 

Online james_s

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #1 on: March 26, 2018, 06:01:49 pm »
What happens if you want to measure a voltage higher than about 75V? I don't think a neon bulb is going to offer a whole lot of protection either. When I was a kid I got a NE-2 and did not yet know about the need for current limiting. I poked the leads into the end of an extension cord and plugged it in, *bang*! The bulb turned completely silver-black and bounced off the ceiling, the leads had completely vaporized.
 

Offline joeqsmith

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #2 on: March 26, 2018, 11:48:39 pm »
Rather than trying to put neon bulbs in your meter, it may be time to think about getting a better meter. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline maginnovision

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #3 on: March 27, 2018, 01:04:17 am »
You probably don't get a neon lit meter with a better meter though. That's the kind of stuff you rely on the makers for.
 

Offline joseph nicholas

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #4 on: March 27, 2018, 01:05:01 am »
I keep buyin um they keep breakin.  Mostly they get damaged because of operator error.  It always seems to involve high voltage which of course one is told not try to measure.  I though about this when someone suggested that a neon bulb could be used to detect a kick back from a choke when the magnetic field collapses.  Anyway I liked the idea of using this as a high voltage surge suppressor.
 

Offline blueskull

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #5 on: March 27, 2018, 01:07:01 am »
Get a neon bulb, stick it into wall socket, and watch it explode and glass shreds flying everywhere. Then tell me if you still want it in your DMM.
 

Offline Brumby

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #6 on: March 27, 2018, 02:06:24 am »
Yeah .... When you see neons across the mains, there's a reason they have a 100K series resistor in place.
 

Offline joeqsmith

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #7 on: March 27, 2018, 02:36:21 am »
I keep buyin um they keep breakin.  Mostly they get damaged because of operator error.  It always seems to involve high voltage which of course one is told not try to measure.  I though about this when someone suggested that a neon bulb could be used to detect a kick back from a choke when the magnetic field collapses.  Anyway I liked the idea of using this as a high voltage surge suppressor.

I'm curious what specific meters you have bought and broke with your high voltage choke transients?   It would be interesting to know what the test setup was that damaged them as well.   If you have something documented that was known to damage one of your meters, I could attempt to replicate it.  Then, assuming it's not some crazy 121GW, I could apply it to the meters I have and see if it damages any of them.   It may give you some idea is there is any meter out there that would survive.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Brumby

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #8 on: March 27, 2018, 03:06:36 am »
^^^ Now THAT'S an offer I'd encourage the OP to take up!  ^^^
 

Offline Fungus

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #9 on: March 27, 2018, 06:48:37 am »
I keep buyin um they keep breakin.  Mostly they get damaged because of operator error.  It always seems to involve high voltage which of course one is told not try to measure.

You can get high voltage probes for that.

(or just make a resistor divider to divide the voltage by 10 or 100 - which is what high voltage probes are internally)

I though about this when someone suggested that a neon bulb could be used to detect a kick back from a choke when the magnetic field collapses.  Anyway I liked the idea of using this as a high voltage surge suppressor.

It may work for very short spikes of electricity on small coils but it's not going to work as a general purpose safety device, because...

Get a neon bulb, stick it into wall socket, and watch it explode and glass shreds flying everywhere.

...this.

There's no current limit so it's going to explode with any sustained current.


 

Offline Fungus

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #10 on: March 27, 2018, 06:52:46 am »
I keep buyin um they keep breakin.  Mostly they get damaged because of operator error.
I'm curious what specific meters you have bought and broke with your high voltage choke transients?

Yep. Are they fancy Fluke meters or are they disposable 830Bs?  :popcorn:
 

Offline joseph nicholas

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #11 on: March 27, 2018, 10:13:22 am »
I just buy cheap meters for China like the DT830 only because the postal delivery here is hit and miss.  I could buy something used like a Fluke but these aren't all that cutting edge like the Aneg multi meters.  What is interesting is what is the difference aside from the obvious between say a neon bulb and a GDT except one is a safety device and one is just an indicator.  They both work in similar ways.  So... just for fun suppose you tried to swap the GDT for a neon bulb.  How would it work?  Would it actually ground a low power surge say from a static discharge or not.  After all you can get 20 of these things for less that 4 dollars on line. I bet they would work for Joe Smiths grill starter test.
 

Offline Gyro

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #12 on: March 27, 2018, 10:26:52 am »
The real differences are:

- Electrode area - GDTs are designed for Arc discharge, much higher current density and different electrode materials. Neons only for glow discharge, much more fragile (as has been indicated previously), they cannot withstand Arc discharge, or even the  'Abnormal glow discharge region'

- Gas composition and pressure are different resulting in:...

-Different breakdown voltage. Neons break down at 70-90V. GDTs are typically specified at 230V (telecom), 1kV etc.

They really are very different beasts.

Edit: Neons would probably work for static but no more.
« Last Edit: March 27, 2018, 10:31:34 am by Gyro »
Chris

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Offline Fungus

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #13 on: March 27, 2018, 10:46:18 am »
just for fun suppose you tried to swap the GDT for a neon bulb.  How would it work? 

Better!

(a GDT is designed to handle several amps, a neon bulb isn't)
 

Offline Brumby

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #14 on: March 27, 2018, 10:49:44 am »
This is the prime difference:
Different breakdown voltage. Neons break down at 70-90V. GDTs are typically specified at 230V (telecom), 1kV etc.

A 90V breakdown voltage is pretty useless if you want to measure 120V.
 

Offline joeqsmith

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #15 on: March 27, 2018, 12:48:17 pm »
I just buy cheap meters for China like the DT830 only because the postal delivery here is hit and miss.  I could buy something used like a Fluke but these aren't all that cutting edge like the Aneg multi meters.  What is interesting is what is the difference aside from the obvious between say a neon bulb and a GDT except one is a safety device and one is just an indicator.  They both work in similar ways.  So... just for fun suppose you tried to swap the GDT for a neon bulb.  How would it work?  Would it actually ground a low power surge say from a static discharge or not.  After all you can get 20 of these things for less that 4 dollars on line. I bet they would work for Joe Smiths grill starter test.

So when I suggest buying a better meter, you would rather buy cheap ones and keep replacing them.  I assume that has not worked out so well for you and replacing meters has become too costly.  Rather than buy a better class of meter, you want to try to modify one with a $0.10 neon bulb to save money.   For now, let's forget about the cost and Darwin awards.   

One thing about a GDT, they will not stop conducting until the current drops to basically nothing.  You put DC across it and if the tube fires it will basically short out the supply.  The MOV will act more like a zener.   You could put a MOV in series with a GDT to get the reset and higher voltages.  I've tested a meter that was designed like this. One thing I have yet to test is a handhel meter where they have placed a clamping device (GDT, MOV or neon buld) directly across the inputs.  There is always a PTC or something there to limit the current.   Even with the cheap ANENG meters you mention.   

The ANENG meter is a bit special in that they actually do have a  clamp right across the inputs.  It's called the rotary switch.  You may feel these meters are cutting edge.  I say they have set back the front end designs to the stone ages..

The grill starter is a very short high voltage transient.  Everything is done and over in under 10ns.  The peak current is much lower than the standards call for.  Hard to say if the neon bulb would do anything for it or not.   Same for putting a MOV across it.   

You are damaging your meters with  some sort of magnetic choke field collapse.  I suspect this transient will have a longer decay, slower rise time, potentially much higher energy and a much lower peak voltage.   I mention this because it sounds like you may feel that if it survives the grill starter, it would survive what ever you are doing. This may not be true.   

Show me what the setup that damaged your 830 and I will get a couple of 830s, attempt to replicate your test, install a neon bulb in the second meter and see if it then survives.  If it does, we will try the piezo grill starter.     If it survives that, I will use the ESD gun I designed.  If all of that survives, we can try the other generators.  Maybe finish the job with that half cycle simulator.    This is what happens to a light bulb when placed across it.   Second video talks about MOVs and GDTs.
 
https://youtu.be/ms5OIBnQ_ig?t=17 

https://youtu.be/wYCGnYglRjY
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Fungus

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #16 on: March 27, 2018, 01:32:11 pm »
I just buy cheap meters for China like the DT830 only because the postal delivery here is hit and miss.

Get a Fluke 101. They cost under $50, delivered. You'll have great difficulty zapping one of those.


 

Offline joseph nicholas

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #17 on: March 27, 2018, 02:44:05 pm »
Thanks for all the answers.  My question definitely got answered and more.  To Joe's inquiry, I though it would be fun to measure the discharge from my stove top electric igniter.  I had a 10x1M series of resistors in a DYI probe but I forgot to use this instead I just hooked it up with a normal probe.  Well needless to say it blew the meter.  These meters  come to me in various states of non function to begin with.  One works on ac voltage but the low ohms range does not, or one works like it should but the buzzer does not.  Well you know the story.  I just tell the seller the problem and he refunds my money. 

The last meter I got I decided to go with the Bside ADM08A because it had a CATIII rating.  Very pleasantly surprised because everything worked except one of the probs was a bit wonky, just needed to have the contacts adjusted.  It cost 20 bucks. No auto ranging, but who cares.  Instead of using it I tried to sell it.  Nobody was interested, they just brought out their Flukes  to show what they already had.  Flukes are the standard here in Mexico.

I really wanted the Aneng, and ordered a few of them, but they never seem to make it here.  The Bside did only because certain Chinese sellers send things over 20 dollars in a different way not through the gov postal system.  I choose the Bside because it was the closest thing to the Aneng I could get with a CATIII rating.  I opened it up and it has proper fuses and even a tantalum cap not an el cheapo but not the DT830 either. 



 
 

Offline janoc

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #18 on: March 27, 2018, 03:13:50 pm »
The last meter I got I decided to go with the Bside ADM08A because it had a CATIII rating.  Very pleasantly surprised because everything worked except one of the probs was a bit wonky, just needed to have the contacts adjusted.  It cost 20 bucks. No auto ranging, but who cares.

If you trust a CAT III rating on $20 meter not being fake (i.e. the meter didn't see an actual test lab even from the plane that brought it into the country) and use it for measuring anything high-voltage or high energy ...  :palm:

Quote
Instead of using it I tried to sell it.  Nobody was interested, they just brought out their Flukes  to show what they already had.  Flukes are the standard here in Mexico.

 :palm: And you think someone would buy a used Chinese special that costs $20 new?

Fluke has kinda religious following among many people but the fact is that their meters are of excellent quality and safe. People don't buy them just to have a $500 toy to show off but because they have only one life. If you are poking the probes into anything connected to mains or high voltage, I would strongly suggest you actually follow their example - doesn't need to be a Fluke, there are plenty of good quality brand name meters in all price brackets on the market (Agilent/Keysight, Amprobe, Brymen, etc).

And if you are breaking so many meters (even cheapo ones), I would strongly advise to step back and look at what you are doing - and why the meters are breaking. That is not normal.

Seriously, you are asking for a Darwin award with your attitude. Not to mention that if you have saved all that money you have wasted on crap meters you could have probably bought that Fluke already.
« Last Edit: March 27, 2018, 03:43:45 pm by janoc »
 

Online james_s

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #19 on: March 27, 2018, 04:46:28 pm »
I bought a Fluke years ago based on their reputation and I'm still using the same meter, it has never had any problems. There's a reason everyone has them, and you've demonstrated why, these cheap meters are mostly crap and by now you have probably spent enough on junk meters to pay for a used Fluke. There are other good meters out there too but none of these no-name Chinese ones are any good, and certainly they don't hold their value like a Fluke, Agilent, etc.
 

Offline joeqsmith

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #20 on: March 27, 2018, 05:25:19 pm »
Thanks for all the answers.  My question definitely got answered and more.  To Joe's inquiry, I though it would be fun to measure the discharge from my stove top electric igniter.  I had a 10x1M series of resistors in a DYI probe but I forgot to use this instead I just hooked it up with a normal probe.  Well needless to say it blew the meter.  These meters  come to me in various states of non function to begin with.  One works on ac voltage but the low ohms range does not, or one works like it should but the buzzer does not.  Well you know the story.  I just tell the seller the problem and he refunds my money. 

The last meter I got I decided to go with the Bside ADM08A because it had a CATIII rating.  Very pleasantly surprised because everything worked except one of the probs was a bit wonky, just needed to have the contacts adjusted.  It cost 20 bucks. No auto ranging, but who cares.  Instead of using it I tried to sell it.  Nobody was interested, they just brought out their Flukes  to show what they already had.  Flukes are the standard here in Mexico.

I really wanted the Aneng, and ordered a few of them, but they never seem to make it here.  The Bside did only because certain Chinese sellers send things over 20 dollars in a different way not through the gov postal system.  I choose the Bside because it was the closest thing to the Aneng I could get with a CATIII rating.  I opened it up and it has proper fuses and even a tantalum cap not an el cheapo but not the DT830 either. 
As I now understand, you have damaged at least one with and electric stove igniter and others with some BEMF transient.   I am not too surprised by the stove igniter damaging one but am still interested in knowing more about the BEMF transients you first mentioned. 

I have seen a few people post besides yourself who wanted to "measure" the output of an igniter.   Again realize that the whole event is over in just a few ns.  Even if it repeats every few ms, the duty cycle would be so small, I am not sure what you would expect to see beyond a dead meter.   I did have someone write to me once how their analog meter could measure ns events. 

Again, forgetting the safety risks and Darwin awards, I did run a few of those cutting edge ANENG meters.  Their poor design (using the switch for a spark gap) allow them to survive fairly well with my tests.  However, I test at VERY low energy levels compared with a CAT III environment.  Something goes wrong there, you won't be limited to 10-20 Joules.   Just something to consider.  It may be possible to get one to survive some basic transients like I run .  Why anyone would ever attempt it beyond for educational or entertainment purposes is beyond me.   This video shows the final changes I had made after destroying four of them.    Again, I would NEVER suggest modifying a handheld meter because of the risks involved.

https://youtu.be/EkQ6CCj7jmU?list=PLZSS2ajxhiQDdiope9HBA8uOD1SbLP5XC
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joseph nicholas

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #21 on: March 27, 2018, 06:54:00 pm »
As I now understand, you have damaged at least one with and electric stove igniter and others with some BEMF transient.   I am not too surprised by the stove igniter damaging one but am still interested in knowing more about the BEMF transients you first mentioned. 

I have seen a few people post besides yourself who wanted to "measure" the output of an igniter.   Again realize that the whole event is over in just a few ns.  Even if it repeats every few ms, the duty cycle would be so small, I am not sure what you would expect to see beyond a dead meter.   I did have someone write to me once how their analog meter could measure ns events. 

Again, forgetting the safety risks and Darwin awards, I did run a few of those cutting edge ANENG meters.  Their poor design (using the switch for a spark gap) allow them to survive fairly well with my tests.  However, I test at VERY low energy levels compared with a CAT III environment.  Something goes wrong there, you won't be limited to 10-20 Joules.   Just something to consider.  It may be possible to get one to survive some basic transients like I run .  Why anyone would ever attempt it beyond for educational or entertainment purposes is beyond me.   This video shows the final changes I had made after destroying four of them.    Again, I would NEVER suggest modifying a handheld meter because of the risks involved.

https://youtu.be/EkQ6CCj7jmU?list=PLZSS2ajxhiQDdiope9HBA8uOD1SbLP5XC
[/quote]

I watch your videos and like your work.

I modify my meters all the time because it just seems like a good way to learn.  I have a DT 9205A, not a bad device if it was in good working order but unfortunately some of the capacitance function did not work out of the box.  I took it apart and got a schematic for it and traced the problem down to one of the two op-amps it uses to do the measurement.  I ordered a replacement ic, I think its a LM324 and when it comes I'm going to replace it and see if it was the problem.  Seems like a great way to work on your diagnostic skills, soldering smd components and reading schematics.  I was scratching my head trying to understand why there were 3 potentiometers and what they did.  One was to adjust the voltage reading (AC and DC), the other two I don't know.  It had a place for an led but it came unpopulated.  So I added it in.  Except for the capacitance function I ended up with a something I can use, it beeps on continuity and flashes an led. 

As to safety:  I have used all my meters even the cheapest junk to measure the 123v ac in my house.  No problem. I measure microwave oven transformers with a 10x`s resistance probe I made for a few dollars.  Works great, and now I have the confidence to measure old CRT flyback transformers safely.  No need to buy expensive things to check high voltage.  Just make them yourself and satisfy your curiosity. 

 

Offline Fungus

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #22 on: March 28, 2018, 06:13:16 am »
As to safety:  I have used all my meters even the cheapest junk to measure the 123v ac in my house.  No problem.

I don't doubt that almost any meter will measure mains if you follow procedure and do it perfectly.

"Safety" is there for when you mess up: We all have bad days.

I invite you to connect one of your junk meters to the mains and turn the range selector through the resistance and diode test ranges. Just for curiosity's sake.  :popcorn:

 

Offline blueskull

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #23 on: March 28, 2018, 07:10:40 am »
I don't doubt that almost any meter will measure mains if you follow procedure and do it perfectly.

"Safety" is there for when you mess up: We all have bad days.

There are a lot of meters in China literally promote on "anti-blowing up" or "protected", and they use a PTC to protect the input so when you put mains voltage into Ohm mode, it won't blow up. More and more Chinese meters are replacing glass fuses with ceramic filled ones, though not HRC rated, they should contain the arc safely even if directly connected across mains.

The true merit I see from a properly designed meter is when mother nature decides to strike a lightning bolt on your upstream power distribution system and sending a CATIII EFT to your power panel. That's when the PTC or depletion FET pair trick won't save you, that's when you definitely want a good MOV and a good HRC fuse if you are in current mode.

And yes, there are mains connected devices using glass fuses, but you don't hold them in your hands when you plug in the power.

After being zapped by 30kV, 33nF a decade ago (along with a few 310V electrolytics) and watched a bunch of photonic induction videos, I'm not gambling on safety.
 

Offline PA4TIM

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Re: Would a neon bulb work in a multi-meter for circuit protection?
« Reply #24 on: March 28, 2018, 08:21:59 am »
Quote
As to safety:  I measure microwave oven transformers with a 10x`s resistance probe I made for a few dollars.  Works great, and now I have the confidence to measure old CRT flyback transformers safely.  No need to buy expensive things to check high voltage.  Just make them yourself and satisfy your curiosity. 

I think it is better to find a safer hobby, like jump from a plane during a hurricane with a DIY parachute made from C-grade Chinese T-shirts.  Or what about Russian Roulette, use a .22 those bullets are small and cheap so it can not be dangerous.... |O

Aneng cutting edge ? More like cutting costs.   :-DD

No problem making things your self, if you know what you are doing. And you have not a single  clue about what you are doing.
Quote
I though it would be fun to measure the discharge from my stove top electric igniter.  I had a 10x1M series of resistors in a DYI probe but I forgot to use this instead I just hooked it up with a normal probe.

Thinking out of the box has nothing to do with it, you are not thinking at all.
Testing things is fun and educational but not this way
« Last Edit: March 28, 2018, 08:24:30 am by PA4TIM »
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