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Old 4th Dec 2019, 12:55 am   #41
The Philpott
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Default Re: Neon Tester Screwdrivers

I am slightly puzzled that i haven't ever seen any upgrades to the basic Neon Tester design. I was browsing on an IET forum earlier and saw that several bods had had similar thoughts, viz:

-Two (or perhaps even three) resistors of equal value in series, mitigating the effect of a resistor failing s/c (a rather unlikely failure)
This would make the tool bulkier, but it could still be acceptably small- especially compared to a voltpen.

- All the internal components potted in clear resin to exclude (as much as possible) accidental water ingress. Would this increase the energy of the shrapnel in the event of a explosive failure of the tester though..? Heading away from electrics towards ballistics here.

I can't really accept that the proliferation of 'better' testers would have halted development to the point where no-one took the opportunity to develop and improve.
....Or are there hidden consequences to the improvements i have suggested?

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Old 7th Dec 2019, 5:01 am   #42
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Default Re: Neon Tester Screwdrivers

I think I've seen 2 resistors in series. I think they also use resistors that aren't likely to short or go low.
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Old 7th Dec 2019, 10:33 am   #43
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Default Re: Neon Tester Screwdrivers

Vintage Engr mentioned
Quote:
BBC-2 colour test film, circa 1967/8
The film with Switch off Isolate Dump and Earth is called "On the Safe Side" It is available on YouTube.
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Old 7th Dec 2019, 3:15 pm   #44
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Default Re: Neon Tester Screwdrivers

Back in the late 1950’s I had a neon tester that had the screwdriver blade cut short and put the rest into a plastic tube, I think resistors came in the tubes, and it was therefore isolated. Used as a guide to tell if line output transformers were working. Only needed to get it within about 2-3 inches and it glowed without having to touch anything.
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Old 10th Dec 2019, 1:58 pm   #45
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by Vintage Engr View Post
That's it, "Switch off, Isolate, Dump, & Earth"

Otherwise you'll be like the poor technician who returns to an H.V. installation, - from a dentist's appointment, only to find out too late that his colleague has reversed the connections of an inductor/capacitor circuit. Big bang!

Anyone remember the BBC-2 colour test film, circa 1967/8?
Sure do, it was one of my favourites and I always stopped work to watch. Mind you, a LOT of them were worth downing tools to watch.
In the TV trade at that time, it was common to wave a neon screwdriver near the line output stage to check if it was doing something. A pretty crude test, but it showed signs of life.
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Old 15th Apr 2020, 10:13 am   #46
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Default Re: Neon Tester Screwdrivers

When I was a meter reader they gave us a Fluke volt stick that had the flashing LED and a beeper in it. Even in bright sunlight you could hear the beeping if it went off.
The only issue I had was if I read a meter under where there was high tension lines or in mobile phone tower control rooms.
These would set the thing off in your pocket so you couldnt tell if the meter box was live or not
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Old 16th Apr 2020, 10:08 pm   #47
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by The Philpott View Post
'All the internal components potted in clear resin'
That's pretty much what an Approved Seaward KD1E HV tester consists of: chain of potted resistors and a neon visible through a window. Except the Seaward tester has to be earthed.

A long time ago I once saw that our DNO (NORWEB back then) used a neon HV tester on V/T circuit spouts that DIDN'T need to be earthed.
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Old 17th Apr 2020, 11:17 am   #48
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by Mullard_Nut_74 View Post
When I was a meter reader they gave us a Fluke volt stick that had the flashing LED and a beeper in it. Even in bright sunlight you could hear the beeping if it went off.
The only issue I had was if I read a meter under where there was high tension lines or in mobile phone tower control rooms.
These would set the thing off in your pocket so you couldnt tell if the meter box was live or not
Rail firms had a similar problem with high impedance digital meters when working under 25KV. The meter would give a reading with no input connected. Solution- provide a 150kohm shunt on th meter input. But come BSI, each meter had to be equipped with it's own shunt and each calibrated as a pair.
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Old 17th Apr 2020, 11:35 am   #49
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by evingar View Post
Quote:
Originally Posted by TonyDuell View Post
I was taught 'All wires are live until _you personally_ have proved they are not' I would never joke about isolating a circuit, but if you are working with me, I would not be insulted if you verified that. In fact I would expect it. Similarly I would hope you would not be insulted if I check the wires were dead. Anyone can make a mistake...
Standard procedure is to isolate the mains and lock off. In front of the person who is going to do the work test the tester with the proving unit. Test all phases and neutral with respect to one another and then with respect to earth. Again, check the tester with the proving unit and hand the person doing the job the lock off keys. If the person doing the work wants to double check that's fine.
That's correct.

Very few in the trade use neon screwdrivers.
These tradesmen are still alive.
They use rated DVMs and Test Sets.
If these are not available, work stops.

Most employers ban screwdrivers.
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Old 18th Jun 2020, 6:31 pm   #50
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by TonyDuell View Post
I was taught 'All wires are live until _you personally_ have proved they are not' I would never joke about isolating a circuit, but if you are working with me, I would not be insulted if you verified that. In fact I would expect it. Similarly I would hope you would not be insulted if I check the wires were dead. Anyone can make a mistake...
Back in my BBC days one of my tasks was to isolate and earth down 11KV enclosures so the tech could go in and do maintenance. One wise old tech watched me calmly as I went through the process for him, opened the door and handed him the keys. Then he said "Well if it's dead, you go and put your hands on it". That really made me think and I've never forgotten that lesson.
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Old 18th Jun 2020, 7:59 pm   #51
The Philpott
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Default Re: Neon Tester Screwdrivers

I did catch someone stirring their coffee with a Neon Screwdriver recently. It retaliated by puncturing the cup and flooding the desk.
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Old 19th Jun 2020, 4:37 pm   #52
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Default Re: Neon Tester Screwdrivers

A neon screwdriver will work with DC mains, unlike the more modern "voltstick" type of non contact testers which are strictly AC only.

DC mains are virtually extinct in the UK, but might still exist overseas.

I know of at least two UK installations with 250 volt batteries.
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Old 19th Jun 2020, 4:49 pm   #53
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Default Re: Neon Tester Screwdrivers

(I may have said this before) As a final check I short all the "dead" wires together and then to ground. People have said, "It might go bang". At least I survived to hear it.
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Old 19th Jun 2020, 5:19 pm   #54
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by AnalogueMan View Post
Back in my BBC days one of my tasks was to isolate and earth down 11KV enclosures so the tech could go in and do maintenance. One wise old tech watched me calmly as I went through the process for him, opened the door and handed him the keys. Then he said "Well if it's dead, you go and put your hands on it". That really made me think and I've never forgotten that lesson.
That's exactly what we did when I was SAP on various BBC sites, and what I do now. The SAP isolated it; proved it dead; earthed it; issued the PtW and confirmed it dead.

It is completely fair and reasonable - and a great confidence booster - for the SAP to touch any hitherto live bits in the presence of the Competent Person who is just about to work on it. In fact, the Engineering Technicians about to dive in INSISTED on it!
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Old 19th Jun 2020, 7:18 pm   #55
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Default Re: Neon Tester Screwdrivers

there are still legitimate uses for a neon tester and no other tester will work and that is when testing polarity on a TNCS incomer!
As the neutral and earth only split inside the service head you cannot test between live and neutral and then live and earth to confirm that the live is actually live and not the neutral,in fact there's a tool called a Testoscope for this, basically it is a neon screwdriver but the end hasn't got a screwdriver blade,just a point.
I've been in the industry for over 30 years and this is the only time I would use a neon tester. I've seen them light on a cable that was cut at both ends,purely to induced voltage in the cable I've seen them not light when on a known live because the user had rubber soles on his shoes and was standing on a wooden floor, but the worst one was when an apprentice dropped one in a sink full of water,he dried it off and put it back in the toolbox without saying anything. The electrician got a nasty belt shortly after when he used it to test a ceiling rose.
That said it is a bit like test prods on meters and such GS 38 states they must have no more than 3mm of bare metal showing, that's dangerous at times, I've seen sparks thinking the item they are working on is dead but it turns out the tip of the prod hasn't made contact with the terminal. I like a good 10mm of metal exposed, if you can't handle a probe safely then in my opinion you have no business working on the stuff.
I totally agree with Russel regarding touching stuff as an AP, in my job I quite often have to isolate kit for a strip out and I always, after making sure it is dead, make a point of showing the other workers that it is dead by touching the cables at the terminals, as he said, it gives them confidence in you.
Recently I was working on a third rail system on a certain underground railway, now it runs at 750v and there are two types of tester for this, one is known as the CRID, or current rail indicating device, used to be known as a 'box of eggs', this is 2 boxes with handles that are placed one on the track rail and the other on the conductor rail, perfectly safe. The other is a pair of black tubes about 20mm in diameter with a cable between them, in the end of one are 3 leds. Partway down on each tube is a large plastic collar, this stops you slipping a hand down and contacting the live rail, not a good idea. Anyway we're on this job and the electrical supervisor from the rail company comes down toprove the rail dead, he then pulls an ordinary Fluke tester out of his pocket to test with! Now ok the Fluke will handle the voltage no issues, but he has zero protection if his hand slips, what an idiot.
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Old 19th Jun 2020, 7:57 pm   #56
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Default Re: Neon Tester Screwdrivers

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'...used to be known as a 'box of eggs', this is 2 boxes with handles that are placed one on the track rail and the other on the conductor rail, perfectly safe.
Would this be a box with lamps connected in series, like a giant test-lamp? I remember as a kid watching 'Blue Peter' and Noaksey went down the underground with the night maintenance team, and I saw them using one of those!
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Old 19th Jun 2020, 8:09 pm   #57
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Default Re: Neon Tester Screwdrivers

Quote:
Originally Posted by russell_w_b View Post
Quote:
Originally Posted by philthespark View Post
'...used to be known as a 'box of eggs', this is 2 boxes with handles that are placed one on the track rail and the other on the conductor rail, perfectly safe.
Would this be a box with lamps connected in series, like a giant test-lamp? I remember as a kid watching 'Blue Peter' and Noaksey went down the underground with the night maintenance team, and I saw them using one of those!
That's the one, we still have them on the network, another one we use is a voltstick, there has been a few incidents of people getting shocks off the trackside cabinets that hold the equipment, so now we have to implement 'test before touch' , simply put, before you touch ANY cabinet or box or enclosure you touch it with the voltstick, if it lights you don't touch it and you have to get someone else out.

some rail testers,the first is a very early 'box of eggs' the second a modern self testing version and the third a modern test lamp set for the same thing,note the hand guards
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Last edited by philthespark; 19th Jun 2020 at 8:19 pm.
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Old 20th Jun 2020, 1:09 am   #58
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Default Re: Neon Tester Screwdrivers

I once watched a film about overground live rail trains.
After the power was switched off they put a shorting link across the live and running rails before walking all the passengers from a broken down train to a near by location where a replacement bus was waiting for them.
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Old 20th Jun 2020, 2:37 pm   #59
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Default Re: Neon Tester Screwdrivers

More crowbar than screwdriver I'd have thought.
This and previous threads have probably summed up all there is to know on the subject. Useful, as long as you understand its limitations.
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