Earthed Electronic test gear

[MrsR]

Hi! Guys,
I have a question about earthing my test gear. It comes from last week when I was using a DSO and got a light ELECTRIC SHOCK FROM THE EARTH LEAD on my DSO test leads.
My house was built in 1942 when we bought the house we had an Electrician check the wiring and all was well??
I have been thinking I might earth all my gear to a separate earth lead going to a steel peg in the ground.
This would only be the gear hooked up to 2 Two 4 outlet boards that are connected to a twin powerpoint. I am not disconnecting the earth on the  power point just by passing that earth and putting earths on the 4 outlet boards.

THANKS
Rachael

[skipjackrc4]

Are you sure it wasn't just ESD?

[Mr.B]

If I understand you correctly, I think you may find that what you propose is not legal in a Multiple Earthed Neutral (MEN) regulated system as we use in New Zealand and Australia.

New Zealand takes a lot of its regulations from Australian standards and I am certain you cannot do that here.
NZ Regs: http://www.legislation.co.nz/regulation/public/2010/0036/latest/DLM2763501.html?src=qs
Wiki description of Earthing Systems: http://en.wikipedia.org/wiki/Earthing_system

I may be wrong... Any registered electricians in NZ or Aus that can shed any light on this?

[Someone]

The current must flow through you to feel a tingle, it is unlikely your earth connection at the power point is faulty but it is possible. What else were you in contact with at the time you felt the sensation? Something had a potential large enough different to the ground of the scope that you felt it, a separate faulty appliance/item is the likely problem.

Due to the commoditisation of electrical safety testing you can get a competent person to come to your house and check the cords and appliances cheaply, the common term used is "test and tag". Once all the appliances are checked to be ok then you could consider the more expensive call for an electrician to check the power points.

[tautech]

Someone has a good point, but you can do some simple earth continuity tests of your cables and power-boards yourself.

A further test for piece of mind would be a quick check of your mains earth possible floating voltage by inserting some sort if metal peg in a wet area and running a wire to your work area for a simple mains earth to GND voltage measurement.
I would be concerned if it is more than a few volts.

[Rerouter]

Another thing that happens with older houses, and why the multiple earthed nuetral system was brought in is the earth connection can go open circuit (joints failing or going resistive with age) so all the EMI rejection caps in modern power supplies will be leaking a few mA on to this earth wire meaning you can get a zap / tingle

though i would not normally recommend any of the general public play with an outlet, you can check the AC voltage between earth and neutral with a decent multimeter to see the difference is almost 0, if its not, you have an issue,

[G7PSK]

Get yourself an Australian version of one these http://www.ebay.co.uk/itm/240v-Mains-3-pin-UK-house-wiring-plug-in-socket-correct-polarity-tester-checker-/310985803520?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item486832c700

They are cheap and give a quick indication of any faults on a socket.