Project

OhmPi: An open source resistivity meter

Goal: This project presents the development of a low-cost, open hardware resistivity meter to provide the scientific community with a robust and flexible tool for small-scale experiments.

Date: 1 January 2018

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Rémi Clément
added 2 research items
A major research effort in recent decades has led to the development of multi-electrodes, multi-channels, accurate, robust and versatile resistivity meters. This work has contributed to the emergence of the electrical resistivity tomography technique and has led to major advances in many fields such as geosciences or the environment or civil engineering. The main limitation of this equipment does not lie in its quality or robustness in the field. It concerns the cost of the equipment and its low adaptability for specific scientific problems. For these reasons, the method is underused for humanitarian applications, in developing countries and for non-profit applications (archaeology, environment). In the field of environment, civil engineering or geosciences, geophysical monitoring has become a key to assess natural systems and phenomena. For these problems, the immobilisation of one or more resistivity meters is not always technically and financially possible. Finally, many applications today require the ability to control the measurement with external nformation and thus optimise the measurement in the context of a “big data”. The OhmPi project aims at proposing an open source hardware and software resistivity meter to the community and the academic world.
Rémi Clément
added an update
We are currently testing a new Plug and Play card for Ohmpi, for 4 electrodes measurement. This board will be the basis for Ohmpi 2 which will be able to integrate up to 128 electrodes. It will be added to the documentation soon!
 
Rémi Clément
added an update
Bugs have been fixed, please update your code (https://gitlab.irstea.fr/reversaal/OhmPi/-/tree/V1.02) and follow the new documentation(https://reversaal.gitlab.irstea.page/OhmPi/V1_02.html). The version 1.01 is out of date.
Fixed bugs:
  • Correction of the electronic diagrams for a better operation of the LM358N operational amplifiers, addition of the capacitors C1, C2, C3 and C4.
  • To limit the underestimation of Vmn in some cases, addition of two DC/DC converters
  • Adds 4 additional resistors to limit the overheating of the components outside the measurement periods.
  • Added the ohmpi_param.json parameter file
  • Added auto-gain function for a better measurement of potential and current.
 
Rémi Clément
added an update
First field installation of OhmPi resistivity-meter on aerated treatment wetland (constructed Wetland) with Pascal Molle and Nicolas Forquet for long-term monitoring!
The system is installed on the experimental platform Reflet( https://reversaal.inrae.fr/nos-outils-experimentaux/nos-plateformes/reflet/)
We have installed buried electrodes on a rigid PVC rack.
The objectives are to follow :
- The evolution of the porous medium by temporal geoelectric monitoring in a constructed wetland, to study the life of the system and the clogging effect.
- Studying the air distribution when the treatment wetland is aerated
Measures will start at the beginning of 2021!
 
Rémi Clément
added an update
OhmPi's documentation is now available https://reversaal.gitlab.irstea.page/OhmPi/index.html. New improvements and fixes will be added in the documentation.
 
Rémi Clément
added 2 research items
Le développement de la tomographie de résistivité électrique et notamment l'amélioration des outils de traitement en suivi temporel, rend la méthode de plus en plus attractive pour le suivi de pilote de laboratoire. Cependant il existe peu d'équipements adaptés aux études en laboratoire en suivi continu. L'objectif de l'article est de présenter les premiers essais de développement d'un résistivimètre sur la base d'une plateforme de développement Arduino. Le système développé présente l'avantage d'avoir un coût faible et d'être facilement contrôlé par différents types de capteurs externes.. Mots clés : Arduino, résistivité électrique, open-source. ABSTRACT Development of electrical resistivity tomography and including improving treatment in time-lapse monitoring tools, makes the method more in more attractive for the laboratory application. However there are few adapted facilities to laboratory in time-lapse studies. The purpose of the article is to present the first tests of development of a resistivimeter based on Arduino development platform. The developed system has the advantage to have a low cost and easily be controlled by different types of external sensor.Titre traduit en anglais
The use of electrical resistivity tomography in laboratory or field experiments for environmental purposes has been increasing in recent years. The development of commercial devices has thus far focused on the quality of measurements and their robustness in all field cases. However, both their costs and lack of flexibility to adapt to specific applications have limited their prevalence in the environmental sector. This article presents the development of a low-cost, open hardware resistivity meter to provide the scientific community with a robust and flexible tool for small-scale experiments. Called OhmPi, this basic resistivity meter features current injection and measurement functions associated with a multiplexer that allows performing automatic measurements with up to 32 electrodes (at a cost of less than $500). The device was first tested using a soil-analog electrical circuit to verify the reliability and robustness of the measurements. Results show that OhmPi offers a wide range of resistance measurements, from 0.2 to 1,000 ohms, for contact resistances between 100 and 5,000 ohms. Measurements were then carried out on a small field experiment, in demonstrating good stability of the OhmPi measurements, as well as a strong correlation with the output of a commercial reference instrument.
Rémi Clément
added a project goal
This project presents the development of a low-cost, open hardware resistivity meter to provide the scientific community with a robust and flexible tool for small-scale experiments.