Envelope-to: dave@picks.force9.co.uk
Delivery-date: Tue, 15 Nov 2005 11:01:43 +0000
Message-ID: <000901c5e9d2$c0cd9670$1f03210a@Hugh>
From: "Hugh M0WYE" <m0wye@thersgb.net>
To: rsgb_lf_group@blacksheep.org
References: <000a01c5e938$ec8c8680$0400a8c0@router> <000501c5e93d$83feadf0$1f03210a@Hugh> <1132001620.4378f95428c87@webmail.ukonline.net>
Date: Tue, 15 Nov 2005 10:52:51 -0000
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Subject: Re: LF: Re: How measuring Ground conductivity ?
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Hello Bryan,
Yes. 10s is twenty or thirty meters.
I designed and built a bit of kit for the purpose of doing some
archeological ground resistance surveys, (although in the end we were able 
to use professional
equipment from the Kent Archeological Society). I tried a frame with four, 4
inch nails spaced 0.33m apart, in a line, and aerated the the back garden
with it. I found it quite a good random number generator from about 10 ohms
to 60 ohms.

I remade the frame with two nails spaced 1 metre apart, one measuring and
one driven, and using a long cable placed the other two probes well outside
the area being surveyed. This gave a much more consistent reading of about
10 ohms, except near the garden path where the reading was higher. This is
the configuration usually employed by archeologists as it is supposed to
"see" deeper into the soil.

My measuring current was 1mA and the polarity reversed at 66Hz.

You are right that the reading doesn't seem to vary much with probe
spacing - a fact which still amazes me.
My, very limited, knowledge comes mostly from the excellent book "Seeing
beneath the soil" by Anthony Clark.

But as John has already observed, the parameter that we are measuring has
only to do with the ground rod effectiveness, and is not a measure of RF 
losses.
73
Hugh M0WYE

----- Original Message ----- 
From: "captbrian" <captbrian@ukonline.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, November 14, 2005 8:53 PM
Subject: Re: LF: Re: How measuring Ground conductivity ?


> What does s stand for as in 10s of meters ? *(Presumably metres)*
>
>
> I thought distance apart made no difference in homogenous soil ?
>
> Bryan (Floating in a boat on sea-water )
>
> Quoting Hugh M0WYE <m0wye@thersgb.net>:
>
>> .
>>
>> However I got similar readings to you - around 10 ohms - with moist,
>> garden
>> soil.
>>
>> I found the most repeatable readings were when one current and one
>> voltage
>> probe, 1m apart, were seperated by 10s of meters from the other pair - as
>> is
>>
>> used for archeological ground resistance surveys.
>>
>> 73
>> Hugh M0WYE
>>
>>
>> ----- Original Message ----- 
>> From: "Uwe Wensauer" <uwe.wensauer@gmx.de>
>> To: <rsgb_lf_group@blacksheep.org>
>> Sent: Monday, November 14, 2005 4:31 PM
>> Subject: LF: How measuring Ground conductivity ?
>>
>>
>> To discuss
>>
>> Measure ground conductivity.
>>
>>
>> I placed two stainless- steel rods ( 3mm dia ) whithin a distance of  7
>> Meters apart abt 80cm deep into soil
>>
>> Powered with 50 Hz.
>> In series with the electrodes is a 10 Ohm resistor. In order to measuring
>> current, I measure the voltage drop across resistor.
>>
>> Depending on weather I got 8 Ohm / m = 125mS
>>
>> Is this measurement setup ( proceeding ) correct ?
>>
>> Please correct me.
>>
>> Uwe, DK1KQ
>>
>>
>>
>>
>
>
> -- 
>
>
> ----------------------------------------------
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