Talk:Test light

Proposed merge from Electrical tester pen

Merging sounds like a good idea to me. Both articles are kind of thin on content, and would be stronger if combined. Also, the proposed direction of merger is appropriate, since Electrical tester pen is a type of Test light. Reify-tech (talk) 17:45, 16 August 2011 (UTC)

Oppose. These are fundamentally different devices and (under UK law at least) they have a different legal status. A test light is a reliable device, used by professional electricians and subject to quite extensive rules to maintain its reliability (i.e. if it doesn't light up, that will be because the circuit is demonstrably safe, not just because the lamp has failed). A neon test screwdriver is something unreliable used by amateurs to lure them into touching live contacts.

As these will probably end up merged (Wtshymanski will just go ahead and do it, no matter what anyone else says) then we should at least make the distinction between the two forms very clear. Andy Dingley (talk) 22:03, 16 August 2011 (UTC)

Is this a real objection or just anti-Bill-ism? How are professional bulbs exempted from the slings and arrows of outrageous fortune that afflict the bulbs we duffers risk our lives upon? --Wtshymanski (talk) 00:31, 17 August 2011 (UTC)

It's a weak objection to merging, more a concern that we don't merge the description of two different devices within that article. One of these is reliable (which means it has to be well made, expensive, and to have formal checking procedures associated with its use) and the other is a death-trap. People regularly get shocked, if not killed, because they've trusted a neon scredwriver to tell them something was safe and it wasn't.

As to article structure, then I think test light should cover screwdrivers, but there is still scope for a lightweight article that covers neon test screwdrivers separately. Many readers will be looking for those, looking for those alone, and they don't need to be force-fed a much bigger article in its entirety.

Other points that should be included on test light would be their use on car electrics (a low-impedance test light often shows up corroded-connector faults than a high impedance voltmeter will miss) and also their narrow, but interesting, use on the London Underground where a multi-lamp box (reliability again) is used to show if the third rail conductor has been isolated safe during nighttime track maintenance work. Andy Dingley (talk) 13:02, 17 August 2011 (UTC)

First, it's not just the third rail but the third and fourth rail.

Secondly, the multi-lamp feature is nothing to do with reliability. The box consistes of three standard mains voltage neon indicator lamps wired in series. This allows the box to be connected direcly across the 630 volts between the third and fourth rails. It was purely a matter of using off-the-shelf parts. The indicator boxes were very short lived and totally removed from the system within a year. I B Wright (talk) 17:25, 27 November 2012 (UTC)

I'm looking for references but the American Electrician's Handbook is (not surprisingly) not au courant with the recent state of the art. References about reliability of test lights would be appropriate, but any tester I've ever seen an instruction manual for has always said "Test on a known live circuit, test the circuit you plan to work on, test again on a known live circuit", not relying soley on the reliability of the test lamp. (This was the protocol the one time I saw a statiscope-type lamp used on 13.8 kV, for example.) I think a discussion of the contrast between the two classes of device would be useful here, especially if we can document OSHA statistics or other reliable source showing the nature of the problem. "Death trap" is perhaps a little extreme, don't you think? Every Home Depot and Canadian Tire sells test lights, either of the neon-bulb-and-two-leads variety, or the non-contact "voltage detector" pen type; yet you can't buy a Hilti gun there. --Wtshymanski (talk) 13:16, 17 August 2011 (UTC)

A UK test lamp means one of these [1] (everyone uses this same design) and it has to meet the IEE 17th edition regs, GS38 in particular. There are two safety aspects to such a lamp - firstly that it reliably indicates voltage (as you say, mostly by testing it before and after, which might require using a proving unit [2] that costs more than the lamp does, even on 240V). Secondly, it must be safe even if when connected to an unprotected circuit, i.e. it can't flow a monstrously huge current, no matter what sort of busbar you drop it across. We did have a notable accident for such not that long ago, where someone was killed by an exploding multimeter.

Neon screwdrivers are unreliable and are a recognised source of accidents. Not usually by electrocution, but by falling off a ladder after receiving an unexpected shock. With the increase in rooftop solar PV installations (vast numbers are going up in the UK right now) there's expected to be an increase in similar accidents. Andy Dingley (talk) 14:07, 17 August 2011 (UTC)

Now this would make a good discussion in an article on test lights. Something like " In response to the concerns about the safety of test lights, the UK Health and Safety Executive require test lamps for use by electricians to be constructed with features described in Electrical Test Equipment For Use by Electricians GSE 38 (revised) . Probes must be well-insulated with finger guards to prevent accidental contact with live terminals; test lights must have a current-limiting fuse or current-limiting resistor and fuse, and must not expose live wires if the test lamp glass bulb is broken." or something on that order. I note the catalog has a lot of spare parts for the test light. GSE 38 doesn't mention anything about the "volt pens", and also doesn't give a threshold minimum voltage that must be detected. If it's a neon lamp, it may not give any visible light even if 60 or 70 volts are on the wires. --Wtshymanski (talk) 16:17, 17 August 2011 (UTC)

Note that GS38 doesn't have any legal standing in the UK (HSE advice doesn't, they have to get specific acts of parliament to make it so), but there is some peculiar legality over electrical regulations where legal definitions of behaviours that must be followed are "outsourced" to the IEE and so their current edition of the wiring regs (the "17th edition") is considered to have full legal standing in a court of law (Mind you, IANAL).

The fuss about test lamps these days (and why you need a real one, not just a voltage tester) is not about insulation, but about protective impedance. This means that when you plug it directly into the back of a power station, the energy delivered to the meter is still insufficent to cause harm. A multimeter, even a fused one, is inadequate to do this, in the case of working on low-impedance supplies with no overcurrent protection. Andy Dingley (talk) 16:27, 17 August 2011 (UTC)

So HSE can't "require" but only "recommend"? Do shops in the UK not also sell the "two phone tips wired to a neon bulb in a plastic case" type of lamp also? Checking an extension cord or wall socket is aboutall you'd want to use one of those for, and I don't doubt that anyone going into an industrial distribution panel needs the current limiting quality. --Wtshymanski (talk) 16:40, 17 August 2011 (UTC)

The HSE can only recommend, but they have friends in parliament who require on their behalf.

I've never seen a UK neon tester that wasn't shaped like a screwdriver and that relied on a return through the user's body. Even for car electrics, testers are generally a single rigid prod in a vaguely screwdriver-like handle, with just one flexible lead as a return. A few years ago we started to see probe meters, like a single fat test prod with a separate return prod on a flexi lead, which are useful for people who either can't afford a Fluke meter, or who keep driving trucks over their good meter.

We don't check wall sockets very often (ring mains means that they rarely fail or blow fuses, as our fuses are in the appliance plugs). If you do check a socket, it's usually with three neons (delta across L-N-E) in a dummy mains plug. This reports L-N crossover errors (a big concern) or crudely disconnected earths and it's also much easier to insert into a shuttered socket. You can buy one of these for under £10. For about £40 you can now get a similar device that also reports roughly on earth loop impedance - a really useful device for touring musicians and their roadies. My big tester (adequate for installation work, with paperwork) cost me a few hundred S/H and £50-ish annually for recalibration. This measures "Megger" insulation resistance with a 1kV test voltage, also low impedances for checking loop continuity, earth impedance per the prescribed magic ritual, and also RCD times for different fault currents. Andy Dingley (talk) 17:17, 17 August 2011 (UTC)

Support. I think Andy's concerns are valid, and should be worked into the merged article. In the US, I've always been aware of the reliability issue, and am careful to pre-test and post-test the tester itself, but I didn't know that the Brits have actually formalized the requirements for a professional-level tester. This fact is certainly notable, and should be explained at least to the extent it is explained here. The quality and reliability difference between cheap $1 testers and professional testers (costing how much?) is certainly worth a sentence or two.

The low-voltage 12VDC testers need a separate subsection, and various other specialized test lamps can be covered in another subsection. The issue of accidentally dropped/misplaced long conductive probes (e.g. screwdrivers) arises in 12VDC just as much as with 13.8kV; both can cause arc faults or explosions if enough current is available. Reify-tech (talk) 16:01, 17 August 2011 (UTC)

I can buy a 12V test lamp or a neon screwdriver in the pound shop for £1, or maybe £10 from Snap-on. A real 240V test lamp is £35-£40.

The accident issue isn't about dropping a spanner across the busbar, it's about current through the tester - impedance, not insulation. Andy Dingley (talk) 17:20, 17 August 2011 (UTC)

Note that the preceding comment was clobbered by an overriding edit. When saving an edited page, please pay attention to and politely resolve "edit conflicts" (in the Wiki technical sense, not editorial disputes). Reify-tech (talk) 17:05, 17 August 2011 (UTC)

A quick Google search shows at least one DIY store chain in the UK is offering the neon screwdriver type. Do we really help the reader by stating that more expensive goods are often better quality than cheaper goods? Some statistics on the number of injuries and fatalities caused by neon screwdrivers would be useful, though I suspect with only on the order of 30 UK electrical fatalities of all kinds per year, there may not be enough incidents with neon screwdrivers to make any noteworthy statistics - I wouldn't care to guess how many million neon screwdriver testers have been sold in the UK. Writing about the hazards of using a 12 volt tester should probably have some external citations and should avoid a "how-to" tone. --Wtshymanski (talk) 17:47, 17 August 2011 (UTC)

The HSE Web site did have a spreadsheet describing one incident in 1986 on an off-shore platform where an electrician was injured by setting a neon screwdriver down on some generator terminals. This isn't really the fault of the neon screwdriver, though. --Wtshymanski (talk) 15:15, 18 August 2011 (UTC)

References

Photograph request

We need a photo of a 17th Edition GS38 test light, maybe even in use. --Wtshymanski (talk) 19:19, 17 August 2011 (UTC)

...and the proving box. --Wtshymanski (talk) 13:49, 1 October 2011 (UTC)

Just checked "Commons" again this morning, no photo there. --Wtshymanski (talk) 14:47, 26 May 2017 (UTC)

Merged

Merged. I've tried to get rid of redundancy between the two articles when it showed up in the merge. --Wtshymanski (talk) 14:51, 31 August 2011 (UTC)

Unsourced neon test light hazards

The long exposed shaft provides a shock hazard to the user

Questionable. I've seen a whole bunch on them and none had a "long exposed shaft". One which copies regular screwdriver design can have damaged insulation, but thats too special condition to call an entire class of test light dangerous. Remember, any work elecricricity requires basic safety rules, and the one of them is to inspect your tools before use.

Failure of the resistor and lamp series network can put the user in direct metallic contact with the circuit under test

Untrue. Gas discharge within a neon lamp is a conductor, so lamp failure is not relevant here. And the damaged lamp is an insulator, clearly. Resistor breakdown requires hundreds of kV. So, until neon test light is modified by bypassing a resistor - it cannot put an user in direct contact with live wire. Technical requirements mandates a presense of that resistor (~1MOhm). — Preceding unsigned comment added by 178.140.244.14 (talk) 00:07, 4 September 2012 (UTC)

Vintage test light

Long-long time ago, such primitive test ligts were used by electricians: http://svp.ucoz.com/kontrolnaja_lampa.jpg (this one looks very makeshift) — Preceding unsigned comment added by 178.140.244.14 (talk) 00:26, 4 September 2012 (UTC)

Field detection - electric or magnetic?

Can we source this, either way? Recent changes have made this consistent as detecting an electric field, but the testers I've looked at all detected a magnetic field. Andy Dingley (talk) 14:35, 14 April 2018 (UTC)

We describe the gadget as working off a capacitive voltage divider. I haven't dismantled any of my testers, but they don't appear to have a sensing coil at the tip, instead having just a plate. But this is original research. --Wtshymanski (talk) 14:55, 14 April 2018 (UTC)

Does it only beep when current is going through the wire? That would be a magnetic field sensor, then, and seemingly much less useful than sensing that a conductor has significant voltage on it. --Wtshymanski (talk) 15:37, 14 April 2018 (UTC)

I've just realised I've got both. My telephone wiring sensors do measure the electrical field (they're mostly intended for identifying wires in a bundle - one of them has a numbered readout, as it sensed a coded signal sent from a multi-way coded sender). My mains wiring ones though use a coil in the tip. A very common sort for the UK DIY market is a coil which can detect either metal or live conductors, even a stud detector. Andy Dingley (talk) 19:47, 14 April 2018 (UTC)

The instruction sheet for this Fluke [3] expressly says "electrostatic". A later model than mine, which is a souvenir of a simpler age - mine doesn't beep. The other Santronics one I have says "electrical field" in its instruction sheet [4]. These instruments only detect energized conductors, and don't react to metal only; what you describe sounds different from these two devices. Neither of these are used for identifying wires connected to a test source, just power line voltage. Well, the Santronics says "power company voltage" but I'm certain it would also work for privately generated electricity,too. --Wtshymanski (talk) 22:23, 14 April 2018 (UTC)