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? |
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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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. |
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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:-)
It was £196 cheaper..... |
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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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Mine has that piece of metal. I wondered what it was for.
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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. |
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