You ask: Occasionally I need to make voltage measurements at points in the supply system before the main switch. I know this is hazardous so what can I do about it?
It is possible for you to make voltage measurements before the main switch safely, but you do need to proceed with caution. First ensure you’re wearing the appropriate PPE and, if applicable, have any relevant permits to work. Then check the specification of the meter you’re using. For this application it MUST have a CAT IV rating in line with IEC 61010 and, if you’re working on the usual UK mains supply, this rating must apply at 300V or higher. The new Megger AVO800 series multimeters are rated CAT IV 600V safety rated, so they’re a good choice for this sort of work. And it’s not just the meter you have to think about – you must ensure your test leads have a CAT IV rating at 300V or higher. You might also want to consider additional protection, such as using fused test leads. If a meter or test leads with a lower CAT rating are used and there’s a surge on the supply they could be damaged, leading to false readings, or even more worrying, injury to the user.
For more Made 2 Measure advice from Megger click here.