|
Strange lighting wiring
Hi All,
I have some 12v spotlights in my bathroom. I needed to move one so disconnected it some time ago and have eventually cut the new hole today. Having now forgotten which way it was wired I thought I should check with a multi meter to be on the safe side. It is 3 core and earth and the results (all AC) are as follows With switch off Grey - brown 146v Grey - black 240v Brown - black 76v With switch on Grey - brown 240v Grey - black 240v Brown - black 0v So for this I conclude that Grey is neutral black is perm live Brown is switched live Is this correct ? More worryingly any idea why I am getting spurious voltages when the switch is off? Thanks in advance Lee. |
Strange lighting wiring
On Saturday, 9 November 2019 16:46:37 UTC, Lee Nowell wrote:
So for this I conclude that Grey is neutral black is perm live Brown is switched live Is this correct ? Probably. But it's certainly not 12 volts :-) More worryingly any idea why I am getting spurious voltages when the switch is off? Induced voltage from parallel conductors. With cables having coupling in the order of about 100pf/metre (minimum), it only takes 10m to get a whole 1nF (i.e. 73uA leakage). Digital multimeters (good ones, that is) are about 20Mohm input. If you measure with a good ol' analogue meter you'll probably find a lot lower than [76V]. https://www2.theiet.org/forums/forum...&threadid=3053 See also https://diy.stackexchange.com/questi...-be-at-0-volts Owain |
Strange lighting wiring
On Saturday, 9 November 2019 16:46:37 UTC, Lee Nowell wrote:
Hi All, I have some 12v spotlights in my bathroom. I needed to move one so disconnected it some time ago and have eventually cut the new hole today. Having now forgotten which way it was wired I thought I should check with a multi meter to be on the safe side. It is 3 core and earth and the results (all AC) are as follows With switch off Grey - brown 146v Grey - black 240v Brown - black 76v With switch on Grey - brown 240v Grey - black 240v Brown - black 0v So for this I conclude that Grey is neutral black is perm live Brown is switched live Is this correct ? More worryingly any idea why I am getting spurious voltages when the switch is off? Thanks in advance Lee. Looks right. Cable capacitance plus a modern high impedance meter - use an old lower R one and those stray Vs will fall away. No earth conductor though? NT |
Strange lighting wiring
The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that?
|
Strange lighting wiring
On 09/11/2019 19:21, Lee Nowell wrote:
The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW |
Strange lighting wiring
On 09/11/2019 19:21, Lee Nowell wrote:
The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? Some Fluke's like a few of the 100 series have a special low impedance range designed to combat this kind of phantom reading. When selected the input impedance drops to around 3K. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Strange lighting wiring
On Saturday, 9 November 2019 20:51:03 UTC, Steve Walker wrote:
On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Decent moving pointers were 50k/volt, so 15M on a 300v dc scale, half that on ac. Rock bottom ones were 1k/v so 150k for 300v ac scale. NT |
Strange lighting wiring
|
Strange lighting wiring
On Saturday, 9 November 2019 16:46:37 UTC, Lee Nowell wrote:
Hi All, I have some 12v spotlights in my bathroom. I needed to move one so disconnected it some time ago and have eventually cut the new hole today. Having now forgotten which way it was wired I thought I should check with a multi meter to be on the safe side. It is 3 core and earth and the results (all AC) are as follows With switch off Grey - brown 146v Grey - black 240v Brown - black 76v With switch on Grey - brown 240v Grey - black 240v Brown - black 0v So for this I conclude that Grey is neutral black is perm live Brown is switched live Is this correct ? More worryingly any idea why I am getting spurious voltages when the switch is off? Thanks in advance Lee. If your meter is one of these cheap"mickey mouse" ones. they often give spurious readings. It's on account of the tiny current they draw. |
Strange lighting wiring
On Sun, 10 Nov 2019 07:06:54 +0000, Robin wrote:
On 10/11/2019 03:43, wrote: On Saturday, 9 November 2019 20:51:03 UTC, Steve Walker wrote: On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Decent moving pointers were 50k/volt, so 15M on a 300v dc scale, half that on ac. Rock bottom ones were 1k/v so 150k for 300v ac scale. Well I never knew before that the Avo 8 (with 1000 ohms-per-volt on AC ranges of 100V and upwards) was at least close to "rock bottom" in the moving coil meter market. Generally was lower on AC ranges. For DC, was 20,000 ohms-per-volt. I have one of the last ones manufactured. -- My posts are my copyright and if @diy_forums or Home Owners' Hub wish to copy them they can pay me £1 a message. Use the BIG mirror service in the UK: http://www.mirrorservice.org *lightning surge protection* - a w_tom conductor |
Strange lighting wiring
On Sat, 9 Nov 2019 20:50:58 +0000, Steve Walker wrote:
On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Had tis on a complex circuit: seemed to be from an octal relay, but only about 230V on a DMM. AVO 8 showed about 200-odd, dropped the range and the figure went down, got to lowest range and bit above FA there. Slightly bent fixed contact, little tweak and it was OK. -- Peter. The gods will stay away whilst religions hold sway |
Strange lighting wiring
On 10/11/2019 08:29, Bob Eager wrote:
On Sun, 10 Nov 2019 07:06:54 +0000, Robin wrote: On 10/11/2019 03:43, wrote: On Saturday, 9 November 2019 20:51:03 UTC, Steve Walker wrote: On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Decent moving pointers were 50k/volt, so 15M on a 300v dc scale, half that on ac. Rock bottom ones were 1k/v so 150k for 300v ac scale. Well I never knew before that the Avo 8 (with 1000 ohms-per-volt on AC ranges of 100V and upwards) was at least close to "rock bottom" in the moving coil meter market. Generally was lower on AC ranges. For DC, was 20,000 ohms-per-volt. Indeed - which is still far short of "decent" (as defined above). I have one of the last ones manufactured. Mine was made in the 60s - and the leads are rather inflexible as a result of the copious tape where the insulation has perished. (Me too mean to buy new leads for what is very, very occasional use.) -- Robin reply-to address is (intended to be) valid |
Strange lighting wiring
Yes I'm assuming each light has its own transformer and the wiring is thus
at mains volts. Not sure about the odd colours though. What one needs is a tungsten lamp on a bit of wire. Beats a meter for this stuff any day! grin. Brian -- ----- -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! wrote in message ... On Saturday, 9 November 2019 16:46:37 UTC, Lee Nowell wrote: So for this I conclude that Grey is neutral black is perm live Brown is switched live Is this correct ? Probably. But it's certainly not 12 volts :-) More worryingly any idea why I am getting spurious voltages when the switch is off? Induced voltage from parallel conductors. With cables having coupling in the order of about 100pf/metre (minimum), it only takes 10m to get a whole 1nF (i.e. 73uA leakage). Digital multimeters (good ones, that is) are about 20Mohm input. If you measure with a good ol' analogue meter you'll probably find a lot lower than [76V]. https://www2.theiet.org/forums/forum...&threadid=3053 See also https://diy.stackexchange.com/questi...-be-at-0-volts Owain |
Strange lighting wiring
Brian Gaff wrote:
Not sure about the odd colours grey, black and brown is the new blue, yellow and red for three core cable. |
Strange lighting wiring
I used to have an old TMK analogue meter that had a button that actually put
a fairly large wattage resistor across the probes so you could see what actually happened under a minimal load, and it used to be very surprising on even fairly short runs of wire at 240v ac. Brian -- ----- -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "Steve Walker" wrote in message ... On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW |
Strange lighting wiring
On Sunday, 10 November 2019 07:06:58 UTC, Robin wrote:
On 10/11/2019 03:43, tabbypurr wrote: On Saturday, 9 November 2019 20:51:03 UTC, Steve Walker wrote: On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Decent moving pointers were 50k/volt, so 15M on a 300v dc scale, half that on ac. Rock bottom ones were 1k/v so 150k for 300v ac scale. Well I never knew before that the Avo 8 (with 1000 ohms-per-volt on AC ranges of 100V and upwards) was at least close to "rock bottom" in the moving coil meter market. The Avo 8 is something from the 1930s. A lot changed since then thankfully. 1k/volt is precisely what rock bottom analog meters from the 60s on were. Rock bottom in the 1930s was the watch type moving iron meters, much less than 1k/volt. NT |
Strange lighting wiring
On 10/11/2019 07:43, harry wrote:
If your meter is one of these cheap "mickey mouse" ones. they often give spurious readings. That's not even wrong... With analogue meters, the better the quality, typically the higher the input impedance. This is in the majority of measurement circumstances a desirable characteristic since it reduces the parasitic effect of the meter on the circuit under test. With digital meters the input impedances are typically significantly higher. Again in many cases this is a "good thing", although it is a trap for the unwary with "floating" circuit cables in close proximity to mains voltages. It's on account of the tiny current they draw. An ideal meter would draw no current at all when measuring voltage. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Strange lighting wiring
In article ,
wrote: On Sunday, 10 November 2019 07:06:58 UTC, Robin wrote: On 10/11/2019 03:43, tabbypurr wrote: On Saturday, 9 November 2019 20:51:03 UTC, Steve Walker wrote: On 09/11/2019 19:21, Lee Nowell wrote: The meter is an old (circa 30 years) fluke meter. Good quality but old. There is earth at the junction box - should I run some more reading with that? A 30-year old digital meter will probably be 20M or more, while an older, analogue meter might be 10K. SteveW Decent moving pointers were 50k/volt, so 15M on a 300v dc scale, half that on ac. Rock bottom ones were 1k/v so 150k for 300v ac scale. Well I never knew before that the Avo 8 (with 1000 ohms-per-volt on AC ranges of 100V and upwards) was at least close to "rock bottom" in the moving coil meter market. The Avo 8 is something from the 1930s. The AVO 8 came out in 1951 and stayed in production until 2008 -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
Strange lighting wiring
In article 07c01b02-2b0f-4c66-9f1d-
, says... On Sunday, 10 November 2019 07:06:58 UTC, Robin wrote: On 10/11/2019 03:43, tabbypurr wrote: Well I never knew before that the Avo 8 (with 1000 ohms-per-volt on AC ranges of 100V and upwards) was at least close to "rock bottom" in the moving coil meter market. The Avo 8 is something from the 1930s. A lot changed since then thankfully. 1k/volt is precisely what rock bottom analog meters from the 60s on were. Rock bottom in the 1930s was the watch type moving iron meters, much less than 1k/volt. When I started work in a TV service department in 1960, all the meters were AVO 8 models. All service data quoted 'all readings taken with 20k/volt meter', which is what the AVO 8 was. However, looking at info for sets we were still repairing, the voltages had obviously been taklen using its predecessor, the AVO 7. This points to the AVO 8 being introduced around the mid 50s The above relates only to the DC ranges, of course. The AVO 8 was regarded as the top of the range and had a price tag to match - certainly well out of my league. My first meter had a similar specification but not the mechanical robustness, nor the 'bombproof' cut-out protected movement of the AVO but it served its purpose well. I may still have it around somewhere. -- Terry |
| All times are GMT +1. The time now is 11:48 PM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter