Soil resistivity measurement

Resistivity, measured in Ohm-centimetres, is the resistance across the opposite faces of a cubic centimetre of a material or, if measured in Ohm-metres, across the opposite faces of cubic metre of a material.
The resistivity of the ground can have a great influence on the corrosion rate of buried metals.
A high value of resistivity will impede the flow corrosion current in the soil, similarly a higher rate of corrosion would be expected in an environment of low resistivity.
Any material with a resistivity value less than 2500 .cm can be considered aggressive.

Principle of survey

The resistivity of soils is measured usually using the WENNER 4 pin method.
The resistivity is calculated by measuring the potential difference between two pins placed in the ground at a known distance. Therefor a certain current is induced in the soil using two other pins placed on each side of the potential pins at the same distance.
The calculation is carried out using Ohm's law.

Site equipment

• Resistance Ohmmeter
• 4 metal pins

Survey procedure

Four pins are placed in the ground in a straight line, the distance between each pin being equal and equivalent to the depth of soil to be measured.
Current is applied to the outer pins by the instrument and a voltage drop is measured between the two inner pins. The instrument displays the average resistance of the soil sample.

Data obtained

At each sampled position the resistivity of the soil is measured at given depth, according the customer request.

Processing and presentation of data

Raw data is tra nsferred to computer on completion of each day and the data is checked to verify accuracy and that the equipment was fully functional and to identify any measurement which may require immediate re-survey.

Data collected is normally presented in tabular form.

Manpower and vehicles

A soil resistivity measurement could be undertaken by one operator. Only one vehicle is needed to perform this service.

Advantages of the potential measurement survey

• Provides an insight of the soil resistivity at a certain depth
• The resistivity depth can be easily adjusted
• Provides a guidance for the protection types needen on a buried structure
• Can easily be combined with GPS-mapping.

Please send us attached information request if you want to receive more information on our services and/or used equipment.
If you want to receive a standard offer you can send us attached request for proposal

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