While this technique has been around for around 100 years, the quality of the tools used in determining electrical resistivity have improved greatly in that time. It is possible to find machines that can provide 2D surveys, as well as 3D surveys of the ground. This can provide far more accurate information.
How electrical resistivity systems work
The purpose of the ERT is to measure the resistance in ohms, and to determine just how difficult, or easy, it is for a current of electricity to pass through a substance. It is possible to utilize alternating current or direct current for these tests. One of the things that is important to remember is that the measurements are dependent on the frequency being used, so you need to take care when you are using different techniques to collect the information.
Some of the common substances close to the surface include sulphide minerals, metallic oxides, and clay. These tend to allow an electrical current to pass through them with relative ease. More fluid in the material can alter just how conductive it is, though, which makes these tests very important.
About electrical resistivity systems
ERT, or electrical resistivity tomography is a type of geophysics method that measures the ground surface as a means to measure the resistivity distribution. The data from the machines is then collected through the machine.
Electrical Resistivity System Manufacturers
Manufacturers that make ERT equipment today include PASI, SuperString, GeoMatrix, and Myron L. You should have no trouble finding high quality machines that will help you in your environmental testing work.