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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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15th Apr 2018, 6:20 pm | #1 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,614
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GPO Indicator Gas No5
I recently bought a GPO Indicator Gas No5 in an auction. The instrument is clean and cased but no further information is known. The meter scale reads "Percent Explosive" at the top. I was told it is for sampling the atmosphere in underground spaces before venturing in with tools.
Has anyone any information about these devices?
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Richard Index: recursive loop: see recursive loop |
15th Apr 2018, 8:37 pm | #2 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: GPO Indicator Gas No5
If you're a member of the Telecommunications Hertitage Group, there are lots of documents about this on their resources web site.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
15th Apr 2018, 10:03 pm | #3 |
Pentode
Join Date: Oct 2017
Location: Newton-le-Willows, Merseyside, UK.
Posts: 158
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Re: GPO Indicator Gas No5
Ah, so you've got an IG5 then! We used them a lot when I was at BT, (http://www.jmwlimited.co.uk/IG5_Indi..._Detector.html)
They are pretty robust,they had to be, the quickest way to kill one was to suck water into it, they have a filter that goes in the sampling line to prevent debris and water being sucked into the sensor, they are a handy tool for checking for flammable gas in chambers and cabinets, although iirc they are designed for natural gas and don't like petrol fumes. Somewhere I have my original BT training manual and I'm sure it has the operating manual in it, I'll dig it out and copy it for you. |
16th Apr 2018, 7:36 am | #4 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,614
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Re: GPO Indicator Gas No5
Mine seems to be an early one, it has a canvas case but looks otherwise just like the one detailed in the link above.
I bought it because no-one else wanted it at a tools auction, and I liked it because it has "PERCENT EXPLOSIVE" on the meter dial. That attracted the schoolboy in me!
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Richard Index: recursive loop: see recursive loop |
16th Apr 2018, 9:18 am | #5 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: GPO Indicator Gas No5
In that case I assume you paid somewhat less than the 198 quid in the linked page!
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
16th Apr 2018, 12:14 pm | #6 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,614
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Re: GPO Indicator Gas No5
It was £196 cheaper.....
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Richard Index: recursive loop: see recursive loop |
16th Apr 2018, 12:22 pm | #7 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,614
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Re: GPO Indicator Gas No5
I'd love to see that if you have time!
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Richard Index: recursive loop: see recursive loop |
16th Apr 2018, 1:35 pm | #8 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
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Re: GPO Indicator Gas No5
ISTR that these had a piece of metal hanging down, so that it would cause ripples when it hit water. It was then time to stop lowering the probe before it sucked in water.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
16th Apr 2018, 1:41 pm | #9 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,614
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Re: GPO Indicator Gas No5
Mine has that piece of metal. I wondered what it was for.
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Richard Index: recursive loop: see recursive loop |
16th Apr 2018, 2:44 pm | #10 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: GPO Indicator Gas No5
Yes, that's the sort of price when I start feeling sorry for a vaguely interesting lot on the basis that I've not lost much even if it proves useless.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
16th Apr 2018, 6:36 pm | #11 |
Triode
Join Date: Nov 2016
Location: Frinton on Sea, Essex, UK.
Posts: 45
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Re: GPO Indicator Gas No5
the sensor is a heated wire, in a bridge cct. the resistance of the wire changes when the gas is passed over it thus altering the bridge and changing the display on the meter. they take a load of U2 1.5v batts. the switch and meter will have a batt test position. the sensor is damaged by the petrol vapour that leaves a coating on the wire. there was a filter unit to be inserted in the sensor line if petrol contamination was expected. and yes when a petrol tank in a garage leaks it finds its way into the cable ducts.
you should be able to test it using the gac cooker, just turn it on for a second and then test the air around it. |