On 13.07.2015 08:58, N_Cook wrote:
On 13/07/2015 07:22, John G wrote:
Phil Allison has brought this to us :
Ralph Mowery wrote:


That should be done with any piece of equipment. Practice
with it and learn the odd things about them.

** As Clint Eastwood might have said: " a man's gootta know the
limitations of his test gear ... "


Where I worked there were many wires in a conduit carring 120
volt control voltage. With a digital meter there was so much
induced voltage you could not tell if a wire was really active
or not. You had to put some kind of a load on them. YOu could
take an analog meter and start with a high voltage range and
then switch to a lower range. If the meter stayed in the same
or near the same physical position, it was just showing the
induced voltage. Even with a wire disconnected at each end,it
would still shock the crap out of you due to that voltage.


** Electricians once regularly used 40W bulbs in a protected,
hand held fittings to test if circuits were live - see pic.

https://img1.etsystatic.com/068/0/63...18127_nbxf.jpg




The AC plug was replaced with two probes in the examples I saw.

I guess it was important to test the bulb before each use ...


... Phil


Some used 2 bulbs in paper bakelite tubes wired in series then they
could test line to line or line to neutral with the same device
without worrying about the voltage or about spurious couplings of
mythical voltages like you can get with meters especially Digital
meters.

Once in college Elec Eng Lab, a cotractor wanted to test 3 wires,
rubbed 2 together and closed down whole large building. when asked
our instructor agreed that was not the accepted method. :-?


Is it apochriphal? . I was told that civil engineering
subcontractors, laying new utilities water/sewage/electricity etc in
trenches, would confirm that any power cables they came across that
should be dead , were dead or not. Using a cartridge powered cutting
blade , that was explosively shot across the cable, severing it.

Yep, that instrument used to be called a "Kabelbeschußgerät" here in
Germany. Nowadays they fall under the firearms regulations, which made
them a royal pain in the back end to own and operate, so they're
actively being replaced by remote-operated pneumatic equivalents now.

Dimitrij