Fail safe 230V test equipment

[Dangermike101]

Hello

So i have had issues in the past where someone has used 230v Test equipment to test a unit, and they have left the mains voltage one when the terminals are not connected and there has been a short or electrocution.

Was trying to come up with an idea where the Live is not powered unless the Earth connector is connected?
So maybe a croc clip attached to metal chassis and the Earth terminal plugged in forms a closed circuit which then switches on the live?
So if the earth is disconnected / Croc clip is disconnected then there are no live ends....

Is this even possible?

 

[Nigel Goodwin]

Your question is so vague as to make no sense, and what has an earth connection got to do with it? - an earth connection doesn't really make anything safer, and can even make it considerably less safe (all it does it alter the conditions for what is dangerous, and what isn't).

You've obviously got a specific exact situation in mind - can you post pictures or diagrams?. Assuming this is a service setting, then it's a good idea to connect all 'equipment under test' via a mains isolation transformer.

The main issue here really though, is that untrained, and incompetent, people shouldn't be messing with test equipment or live mains at all.

 

[AnalogKid]

I think the idea is that the earth connection is acting as a sensor to determine electrically that a connector (or wires to a terminal strip) is plugged in mechanically.

Or something like that.

Back in the backplane days (80's-90's, VME, VXI, Multibus, etc.), this was a common technique for one board to tell if another board was plugged in, or for an I/O board to tell if a cable was connected. The problem is this part:

"which then switches on the live"

That sounds like a relay, SSR, or contactor between the mains ("the live") and the connection point. How ans where is that done?

ak

 

[schmitt trigger]

As Nigel mentioned, we need more specific details of the situation…

Equipment manufacturers are not dumb. They are fully aware of the risks of working with electricity. That is the reason that DMM banana plugs are fully shrouded and their tips insulated. That is the reason fuses in current inputs are of the high-capacity arc interruption type. The CAT ratings are a result of industry wide study and consensus.

Of course, there are those ultra cheap DMMs who may not follow those rules.
But again, we require additional details of your individual situation.

 

[Diver300]

There are electrical devices that detect that there is an earth before operating.

 

[kubeek]

...there has been a short or electrocution.

How many people got killed?

 

[rjenkinsgb]

The most basic precaution is to supply your test equipment power via an earth leakage circuit breaker.

If anyone touches a live connection, or if there is a fault between live or neutral and ground (even if the device being tested is ungrounded) the ELCB (aka RCD) should cut the power off before any harm is done.

eg.

SafetySure RCD Socket Metalclad

• Passive (does not need resetting after a power loss)• Conforms to BS7288:1990, BS1363

www.toolstation.com

You can also get more sensitive ones.