PQWT ground water detector: Hardened ground can be measured with plate electrodes.

   As society progresses, hardened ground is becoming more and more common. The new PQWT ground water detector has 22 electrodes, and it is a frequent problem how to measure on hardened ground such as concrete, asphalt, masonry, etc. It is very troublesome to pile up soil and water for each electrode, and it is even more difficult to measure more lines. Especially for cement, asphalt and rock slab pavement, the ground water detector has a very thick layer of secondary ash or dry hard cement bedding underneath, so it is neither possible nor necessary to pour water through for a short time.

   Such hardened ground is shielded if measured by the resistivity method, and each electrode cannot be measured without drilling through, and the current supplied to the ground cannot pass into the ground. Antenna method is the use of natural electromagnetic wave measurement, without the need to supply electricity to the underground. The characteristic of electromagnetic wave is that it is afraid of softness and not hardness, and the more hard layer it meets, the easier it is to penetrate, as long as the conventional rod electrode is changed to "plate electrode", it can be measured well without drilling, without piling up soil.

   We made the following plate electrodes for your reference.

   Cut a 10cm diameter plate from a 3-5mm thick steel plate and weld a handle to it. In order to make the electrode contact with the ground better, water can make the contact surface wetter, a towel cloth can be used to wrap the electrode, rely on the towel cloth (also available thin sponge, accommodating more water) in the water as a conductive body to connect the electrode with the ground. This is a "plate electrode". For multi-channel instruments, 22 plate electrodes are needed (for single-channel instruments, only 2 are needed). After the electrodes are in place, connect the plate electrodes to the clips on the cable with connecting wires (single-channel instruments are connected with copper noses). Then the towel cloth of each electrode and the ground where it touches is wetted with ordinary water can be measured (the resistivity of tap water and the general resistivity of soil are generally less than 100 ohm meters, which is the same order of magnitude. (Water as an intermediary conductor, its contact resistance is uniform and stable, the measurement effect is better).

   The figure attached is a comparison between the graph we measured with the plate electrode on the impermeable rock slab ground and the graph we measured with the conventional rod electrode on the land surface, the ground water detector graph and data are almost identical. To prevent false anomalies, it is better not to alternate hardened ground and ground surface in the same measurement line.

   The ground water detector plate electrode is very easy to do, easy to carry, and can be used permanently, so you may try it.