Beat Meier wrote:
Hi again
Now I really don't understand anything.
Today after raining 2 days I have mesaured again the resistivity (now
107ohm thats ok) and my ground in my house (3 pole method).
The ground in my house is show as 9.47 ohm.
As I wrote earlier I have only 2 2.5m 5/8 ground roads and the
resistivityis 500ohm respectivly 120ohm.
How can this be apart from doing something wrong?
Beat
>Hi all
>
>I'm still a grounding dumy but I've just bought a GEO test and have done
>some soil resistivity test
>(for just 800US$ I can do 4 pole methods, cheapest I have found and
>still has serial port
>to colect data ...)
>I'm still in putting my new tower of 200ft ...
>
>Now I have some questions.
>In a place where I have 2 ground roads (each 2.5m) I have a resistivity
>of 120.
>4m away I have a resistivity of 500.
>The test was done with the 4 pole method.
>I have not measured the ground of the house, only the soil just above
>where the
>roads are with several depth and in the deps of 3 m I have this 120
>
>Now my questions:
>
>1. This low resistivity comes from the 2 ground roads already there
>I have read that 2 ground roads in parallel will half the resistivity
>i..e 500/2 250 but I have 120
>If you use 4 you get Resistividad/4 i.e. 500/4=125
>Is this formula right?
>The other idea is that the fundament of the house is very near (about
>1m) could this also
>have such influence to lower the resistivity because of concret??
>
>2. The resistivity of 500 is not very good, isn't it?
>
>I have calculated that you must put 36 ground roads in parallel to
>achive a resitance of 13.8
>which is still pretty bad (of course only if the formula above is right)
>
>BTW: The tests have showed what someone already told me that the soil
>here is not good
>to go in depth ... I have the following:
>
>a=2m -> 486
>a=3m -> 546
>a=4M ->535
>a=6m -> 429
>
>so it seems that going in deep does not make any difference (apart from
>the cables you must use
>to connect the ground roads) in contrast to use parallel ground roads.
>
>And last question:
>How many copper have good ground roads. The ground roads I can buy here
>have only 200um of copper
>(5/8''-2m or 5/8''-3m). I have seen that they peel quickly if driven
>into earth and there is any obstacle ...
>
>What I can get also is plate of copper 30cmx30cm but this costs about 8
>times more than one ground road
>I don't know how they lower the resistividad of the soil ... I have read
>in an article about
>0.8*Resitivida/circumference is this right?
>
>What about putting using the fundament of the house i.e. drive a whole
>in the concrete and connect a
>copper or what ever cable ot the iron and put again concret?
>
>Thanks for any ideas or comments
>
>Beat
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