What is electrode contact resistance? How can I improve contact resistance?

October 19 2022

One of the most common causes of poor readings in resistivity survey is poor electrical contact at the electrodes which can be seen as high resistance values during the electrode contact test on the Terrameter instruments. The electrode contact can be improved by several different methods, such as using more or longer electrodes or by introducing more conductive material around the electrodes and these will be discussed below.

If the contact resistance at the electrodes is too high, it can cause instability in the measurement. You can use the Electrode Test in the ABEM Terrameter LS2 to identify electrodes with poor contact resistances compared with the others and these problems can be reduced by:

Hammering electrodes deeper (using longer electrodes if necessary); doubling the insertion depth can provide a 40% improvement in contact resistance.

Using more than one electrode at each cable take-out and connecting them together ‘in parallel’ (with cable jumpers); a second electrode can reduce the contact resistance to around 60% of the initial value, adding another will reduce it to 40% of the initial value, adding additional electrodes after this provide smaller improvements.

Using some kind of conductive fluid (water, salt water or electrolyte gel) to improve the conductivity of the material surrounding an electrode; gels can be especially useful for porous materials where regular fluid drains away quickly but they are more expensive.
Use conductive clay, such as bentonite, around the electrodes to increase the effective surface area.
Pushing the electrodes through water-soaked sponges can help to maintain lower contact resistances in hot environments by keeping the ground beneath damp for longer.
Use an alternative electrode design such as plate electrodes.

What is electrode contact resistance? How can I improve contact resistance?

More to read