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Post Time: 10/09/2008 18:39:14 |
patchmac
Total Forum Posts: 2 |
Help please !
I have a situation where electric fields of up to 40v/m are reading over a pillow area. I have installed both a Heath-Robinson chicken wire screen and also subsequently screened with Flectron between the bed and the wall where the field emanates from. Both screens are carefully grounded to the earth pin in the elctrical socket. When I ground the screens by simply holding on to them with my hand, the measured field drops to zero. When I remove my hand and allow the earthing wire to ground the field, there is no drop in the level, which stays around 40 v/m. I had assumed that the socket was inadequately earthed itself, but a competent licensed electrician has assessed the wiring and reports a good ground is present at that socket and also elsewhere throughout the house - he is mystefied as am I. Do you have any suggestioins as to something I'm not thinking about or some other issue that would create this situation ?
Thanks in advance, Patrick MacManaway |
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Post Time: 11/09/2008 22:02:42 |
alasdairP
Total Forum Posts: 173 |
Patrick, you have come across an example of a common puzzling problem.
Basically, electric fields from normal unscreened wiring couple into the building structure. Electric fields are measured between two points (which is why they have units of volts per metre). We believe that they should be measured by the person holding an un-earthed meter as that then measures the electric field they are actually experiencing at that place and time.
If you use and earth lead, then the field measured is the absolute field referred to Earth rather than in relation to any person standing or lying there. When you touch the screening material you short out the effective electric field which then drops to near zero. This shows that YOU are actually the source of the fields, not the wall. You will find a similar effect close to upstairs metal hot water radiators.
Upstairs in a house or flat, most of the electric fields actually come up through your legs (or the bed or chair) from the floor and are due to the downstairs lighting circuit wiring.
By putting Earthed screens on the wall, you usually actually increase the experienced electric fields!!! You need to put an earthed layer of metal or metal foil underneath the bed (or bed legs if the bed stands on legs). Then when you lie on the bed the e-fields to the earthed wall will be low.
Some people install "Demand switches" in the downstairs lighting circuit so that, at night when the downstairs lights are off, the fields emanating from the floor above drop to low levels.
Electric fields can be difficult to assess and remove.
I hope this helps. Do feel free to ask further questions about this. We were delighted to see that you had subscribed. Thanks. We hope you are well.
Alasdair & Jean. |
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Post Time: 04/10/2008 12:59:43 |
patchmac
Total Forum Posts: 2 |
Hello !
very many thanks for your insight and support, will sort as you recommend
all best wishes meanwhile
Patrick MacManaway |
