Samenvatting

Waterschap Scheldestromen is carrying out a particularly innovative project named Multiflexmeter (MFM), of which the objective is to look for ways to measure the soil resistance . This means some properties and characteristics of water needs to be researched on, such as the salinity and the corresponding conductivity. At the request of Waterschap Scheldestromen and Province of Zeeland, in the Netherlands, an automated soil resistance meter (watcher) with switchable electrode set is required to be designed based on previous related research. The working principle of an existing commercial handheld measuring device (Chauvin Arnoux C.A 6460) is regarded as the designing reference. The aim of this project is to develop an open-source measuring system that can automatically measure the resistance of all possible 4-electrode combinations using Wenner method.

The entire project moved forward under the guide of V-model method. The V-model was not applied in this project rigidly, instead, several flexible adjustments had been implemented in order to reasonably adapt this methodology to the actual condition of this project. Following the V-model, the design phase was divided into system design, sub-system design and component design. In addition, main question and sub-questions were raised appropriately.

The core part of the ultimate product of this project is mainly one Printed Circuit Board with 23 optocouplers and a measuring chip on it. Besides that, there are Arduino microcontroller and signal generation circuit externally. The cost of designing, purchasing components and assembly is under 100€, which is within the budget. This system prototype fulfills the task of switching automatically and measuring accurately (errors under 6%) in lab conditions by using 25 ideal resistors to test whilst the system did not fully achieve the expected performance in the field test. The on-site test results were fairly unstable and it was noted that with the test continuing, the accuracy and stability of the system were declining gradually.

There are some possible reasons causing the different performance of this same system under the in-lab conditions and on-site conditions respectively. The corresponding discussion of this part is in Chapter 5 and Chapter 6.

On the whole, further research related to this project is required to find out the exact reasons that lead to poor performance of the system prototype in the field test and the corresponding solutions. Additionally, there is still much room for improvement the system designed in this project. For instance, considering adding intermediate relays is one of the possibilities to optimize it. Also, there will be opportunity for this system to be integrated into the huge-scale Multiflexmeter project system in the future.