EMI
Electromagnetic induction (EMI), which is widely used in near-surface geophysical or agricultural applications, allows for contactless and fast mapping of electrical soil conductivity. Such systems use pairs of transmitter (Tx) and receiver (Rx) coils to measure the very small eddy current effect that depends on the electrical conductivity of the soil. Multiple pairs of coils with different spacing allow to measure different depth ranges of the subsurface up to about 1.5 times the largest transmitter-receiver distance.
The problem is that the measured values of the apparent electrical conductivity (ECa) of EMI systems drift due to thermal effects in the system. However, an accurate measurement of the conductivity is absolutely necessary for the quantitative reconstruction of the depth-dependent electrical conductivity distribution of the subsurface.
To improve the depth resolution a modular measurement system (SELMA), based on previous developments (ELMA3) with a large number (>=12) of freely configurable Tx-Rx coil pairs and improved drift correction is being developed. The coils are mounted in transportable modules that can be coupled to form a system. The modules can be flexible arrangement in x and y direction. High resolution ADCs and DACs are used for the precise acquisition of the measured values.
For drift correction, in situ methods on circuit level as well as model based numerical methods are applied. Furthermore, methods are being developed that enable measurements in environments with electromagnetic interference induced, for example, by vibrations of mechanical parts.
Contact
- Institute of Technology and Engineering (ITE)
Room 229