UFC 3-570-06
JANUARY 31 2003
Table 7-3. Four-Pin Soil Resistivity Measurement Reading Multipliers
Common Distances
Even Multipliers
Distance
Reading
Distance
Reading
Between
Multiplier
Between Rods
Multiplier
Rods
2'6"
479
2'7"
500
5'
958
5'3"
1000
7'6"
1,436
7'10"
1,500
10'
1,915
10'5"
2,000
12'6"
2,394
13'1"
2,500
15'
2,872
15'8"
3,000
20'
3,830
20'11"
4,000
30'
5,745
31'4"
6,000
7-11.2
potential drop is measured between the same pair of electrodes used to supply the
current. The equipment used to make this type of measurement is often called the
"Shepard's Canes," after its inventor. As shown in Figure 7-27, the probes are placed 0.3
meters (one foot) apart. If the soil is too hard for the probes to penetrate, the reading is
taken at the bottom of two augured holes. The instrument is calibrated for a probe
spacing of one foot and gives a reading directly in ohm-cm. Although this method is less
accurate than the four-pin method and measures the resistivity of the soil only near the
surface, it is often used for preliminary surveys, as it is quicker than the four-pin method.
7-43
Previous Page
