AEMC 3640 - Factors Affecting Soil Resistivity

Digital Ground Resistance Tester Model 3640 and 4610 17
4.1.3 Factors Affecting Soil Resistivity
Twosamplesofsoil,whenthoroughlydried,maybecomeinfactverygood
insulators, having a resistivity in excess of 109 ohm-centimeters. The
resistivityofthesoilsampleisseentochangequiterapidlyuntilapproxi-
matelytwentypercentorgreatermoisturecontentisreached.
0
2.5
5
10
15
20
30
> 109
250,000
165,000
53,000
19,000
12,000
6,400
> 109
150,000
43,000
18,500
10,500
6,300
4,200
Resistivity, Ω-cm
Moisture content,
% by weight
Top Soil Sandy Loam
Table 2
Theresistivityofthesoilisalsoinuencedbytemperature.Table3shows
thevariationoftheresistivityofsandyloam,containing15.2%moisture,
withtemperaturechangesfrom20°to-15°C.Inthistemperaturerangethe
resistivityisseentovaryfrom7,200to330,000ohm-centimeters.