10-03-2013, 09:46 AM
In the VHF90 thread by Rob ('Bushbaby'), the topic arose of inadvertently applying voltage to the prods of a multimeter set to the Ohms range. Rather than take Rob's thread off topic, I've started this thread, which harks back to a former life when I spent my career at British Gas. During the forty years I spent there, I saw the role of what were from the 1820s known as 'gasfitters' turned on its head.
We served a six years apprenticeship during which we had to pass the intermediate and final C& G practical and theory exams. If you failed the final, you were given one more attempt and if you didn't pass then, you didn't qualify. You were only allowed to work as a mate, or as a 'maintenance man'. Such people were rather unkindly referred to as ‘dilutees’ in that they were seen as diluting the skills base. Maintaining and repairing gas appliances - sink and bath water heaters (‘geysers’), gas fires and cookers - back then was a simple task. The real skill was in pipefitting – lead (for water and gas), copper, brass, and iron pipe, lead sheet for roofing and flue work and so on, with much to learn connected with gas safety, and in the early stages, working on live gas.
Gradually over time, the pipefitting aspect was de-skilled to DIY level, due to the use of copper pipe, but the maintenance skills became more demanding – cookers began to have electrical controls for spark ignition and flame failure devices on every burner, gas fires too often have electrical controls. But the big change was down to central heating systems. Certainly by the mid 1970s, the role of what were originally 'gasfitters' at British Gas was metamorphosing into 'service engineers' with greater number of central heating systems installed in domestic properties. Their role started to change from being largely based on plumbing skills towards requiring electrical fault diagnosis skills. When a gas central heating system stops working, it is almost certainly due to an electrical fault either on the boiler controls or elsewhere on the system (pump, room thermostat, boiler thermostat). The BG 'engineers' were well trained to use fault finding techniques based on continuity tests rather than voltage tests, but as with vintage valve radios, occasionally it is necessary to establish whether there is voltage present.
Initially, they were equipped with Avo Multiminors in nice hard leather cases. They would stand being chucked about in toolboxes, thrown in the back of a van, but they wouldn't stand having 240V squirted into them on the Ohms range. On average, the AVOs lasted about 3 months before they were fried. Skiploads of Multiminors went to landfill - looking back, I rather regret not 'skip diving'! (They could be repaired by the likes of us if we were inclined to make new shunts). From 1978 - 1990 I was Service Manager for BG at Sheffield, where BG employed some 300 service engineers at the time. It wasn't long before BG commissioned a design for their own multimeter more suited to its needs, rather than what was in essence, an Avo hobbyists meter. The BG meter had probes to check temperatures to help in balancing radiators on central heating systems, and adaptors to check the output in mV of boiler thermocouples - back then, and to some extent still today, often a source of boiler failure.
It's nineteen years since I retired so I'm well out of touch with what BG use nowadays. A cheap Maplin analogue meter is all that's needed if used competently, but when working in tight spaces such as cylinder cupboards, or in roof spaces where boilers are often installed, and when you've already done 15 jobs and worked through your lunch hour grabbing a quick sandwich in the van, I guess three months isn't a bad life for an unprotected multimeter before its luck runs out when some tired engineer squirts 240V into it on the Ohms range. At least he gets an answer - yes, that terminal is live, the meter is now terminal, and as you are mortal, if you touch it, you could be terminal too!
Personally, for central heating systems I find Voltsticks and Magnet sticks more useful than test meters as you don’t need to poke around at any wiring. If you want to know if it’s live (or not), a Voltstick will tell you. If you want to know if there is (or isn't) a magnetic field where you want one (relays, solenoid valves etc), the Magsitck will tell you. Simple, quick, robust, cheap and safe:
http://blog.sparksdirect.co.uk/the-volt-...indicator/
Waffled and dribbled Yorkie, nostalgically.
We served a six years apprenticeship during which we had to pass the intermediate and final C& G practical and theory exams. If you failed the final, you were given one more attempt and if you didn't pass then, you didn't qualify. You were only allowed to work as a mate, or as a 'maintenance man'. Such people were rather unkindly referred to as ‘dilutees’ in that they were seen as diluting the skills base. Maintaining and repairing gas appliances - sink and bath water heaters (‘geysers’), gas fires and cookers - back then was a simple task. The real skill was in pipefitting – lead (for water and gas), copper, brass, and iron pipe, lead sheet for roofing and flue work and so on, with much to learn connected with gas safety, and in the early stages, working on live gas.
Gradually over time, the pipefitting aspect was de-skilled to DIY level, due to the use of copper pipe, but the maintenance skills became more demanding – cookers began to have electrical controls for spark ignition and flame failure devices on every burner, gas fires too often have electrical controls. But the big change was down to central heating systems. Certainly by the mid 1970s, the role of what were originally 'gasfitters' at British Gas was metamorphosing into 'service engineers' with greater number of central heating systems installed in domestic properties. Their role started to change from being largely based on plumbing skills towards requiring electrical fault diagnosis skills. When a gas central heating system stops working, it is almost certainly due to an electrical fault either on the boiler controls or elsewhere on the system (pump, room thermostat, boiler thermostat). The BG 'engineers' were well trained to use fault finding techniques based on continuity tests rather than voltage tests, but as with vintage valve radios, occasionally it is necessary to establish whether there is voltage present.
Initially, they were equipped with Avo Multiminors in nice hard leather cases. They would stand being chucked about in toolboxes, thrown in the back of a van, but they wouldn't stand having 240V squirted into them on the Ohms range. On average, the AVOs lasted about 3 months before they were fried. Skiploads of Multiminors went to landfill - looking back, I rather regret not 'skip diving'! (They could be repaired by the likes of us if we were inclined to make new shunts). From 1978 - 1990 I was Service Manager for BG at Sheffield, where BG employed some 300 service engineers at the time. It wasn't long before BG commissioned a design for their own multimeter more suited to its needs, rather than what was in essence, an Avo hobbyists meter. The BG meter had probes to check temperatures to help in balancing radiators on central heating systems, and adaptors to check the output in mV of boiler thermocouples - back then, and to some extent still today, often a source of boiler failure.
It's nineteen years since I retired so I'm well out of touch with what BG use nowadays. A cheap Maplin analogue meter is all that's needed if used competently, but when working in tight spaces such as cylinder cupboards, or in roof spaces where boilers are often installed, and when you've already done 15 jobs and worked through your lunch hour grabbing a quick sandwich in the van, I guess three months isn't a bad life for an unprotected multimeter before its luck runs out when some tired engineer squirts 240V into it on the Ohms range. At least he gets an answer - yes, that terminal is live, the meter is now terminal, and as you are mortal, if you touch it, you could be terminal too!
Personally, for central heating systems I find Voltsticks and Magnet sticks more useful than test meters as you don’t need to poke around at any wiring. If you want to know if it’s live (or not), a Voltstick will tell you. If you want to know if there is (or isn't) a magnetic field where you want one (relays, solenoid valves etc), the Magsitck will tell you. Simple, quick, robust, cheap and safe:
http://blog.sparksdirect.co.uk/the-volt-...indicator/
Waffled and dribbled Yorkie, nostalgically.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
