[Julesomega]

We all have to work on mains wiring at times. Even if you can afford to pay a qualified electrician to maintain your fittings there will come a time when you cannot wait til next week to have the heating, cooling, or the shower fixed.
That's when you get out the old trusty neon tester screwdriver and rely on it to confirm that you've disconnected the right circuit.
I was called to fix someone's electric shower this week and got out the two neon testers I carry in the toolbox. The sun was shining onto the white bathroom walls which makes neon testing difficult at the best of times and the cheapo small tester did not light up, however the better and larger tester could just be perceived to be lit when touched, which protected me from a bit of consternation.

On the way home I called into a DIY store and bought their good quality tester, branded Wera. This is nicely made, with a proper 150k resistor visible. I love the pocket clip for its elegant simplicity. A reviewer posts as follows: "As an Electrician I would never depend on this type of tester to prove the power is off. I use this screw driver as a terminal screwdriver as it clips into my overall top pocket. To test the power is off a test meter is a must even using a test meter you are advised to test the meter before use and after use to confirm the meter is still working. Electricity can Kill!!"

Dismantling the failed cheapo unit by snapping it open reveals some kind of resistor substitute like a tube of dark crystals which measures o/c ie >10Mohm. The same happened with an identical one I had earlier. DO NOT buy these and throw away any you find.

Speaking of old faithfuls, I still use the Vitrex tester I bought in 1970. The pocket clip has long since broken off and the top is broken off: that used to carry a spare plug fuse and allowed you to test other fuses, blown/not_blown. The blade is indestructible.