In some cases, it is possible to use a flat metal plate type electrode or an absorbent clay or other absorbent material saturated with salt water to form an electrode over concrete and exposed hard rock surfaces
Example:
At this particular station (pictured below), the electrode position was an out crop of crystalline rock. Instead of being forced to skip this electrode position (which is possible in the SuperSting™ Menu 6), sufficient electrical coupling was achieved by using an absorbent material soaked in salt water (absorbent pack or bentonite clay) to keep moisture in place during the survey. In this case, the instrument was able to send out ~20 mA through this electrode which is more than sufficient to achieve a good signal to noise with the SuperSting™ receiver.
Key Points in this Image
•Flat electrode stake
•Absorbent material soaked in salt water on top of stake
•Heavy rocks pressing the stake and material into the outcrop