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Electronic Measurements

Development VES instrument

VES prototype Recently, a prototype of an affordable VES device was developed for use in developing countries on behalf of Practica Foundation. VES - Vertical Electrical Sounding - is a geophysical measuring principle that maps the conductivity of soil layers by means of a current injection into the soil and ground potential measurements. To obtain information about the different types of soil as a function of depth, multiple measurements are made at different electrode distances.
This also provides information about the depth of water and about the presence of rock. A mathematical model is applied on the resistance values in order to obtain a depth profile. VES measurements are necessary to reduce the number of failed costly bore holes.

To date, the low-budget VES measurements were performed by drilling companies by means of a 230 volt inverter powered by a car battery. This voltage is rectified and injected into the ground via a polarity switch and current limiting resistor. This injection current and the ground potential are both measured with multimeters. In the case of low-ohmic soil types such as clay, the inverter is omitted and the battery voltage is directly injected. Because the earth also generates a potential itself, it is difficult to distinguish the signal from its own potential with this method.

The newly developed hardware combines the inverter, polarity and activation switch and the two multimeters into one device. The instrument generates an injection signal whose pattern and polarity are adjustable. The measured current and potential values ??are sampled and sent to a smartphone via a bluetooth connection. The app running on the phone was developed by Mark Tiele Westra from Hiemsteed Media. It ensures the correct settings of the instrument and intuition of the sampled current and voltage.
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