diff --git a/sphinx/build/doctrees/environment.pickle b/sphinx/build/doctrees/environment.pickle
index 333337f84460dcaa361766dfed22ec78737a63f2..b1cd38131d2a1b693079f5faf269eb2e5310253f 100644
Binary files a/sphinx/build/doctrees/environment.pickle and b/sphinx/build/doctrees/environment.pickle differ
diff --git a/sphinx/build/doctrees/page1.doctree b/sphinx/build/doctrees/page1.doctree
index 3f68d8e8b938f0483d75d3ecc93819c80c242bac..096c1d47f3234516ea7d021a544df4c81bcdba06 100644
Binary files a/sphinx/build/doctrees/page1.doctree and b/sphinx/build/doctrees/page1.doctree differ
diff --git a/sphinx/build/html/_images/current_board.jpg b/sphinx/build/html/_images/current_board.jpg
new file mode 100644
index 0000000000000000000000000000000000000000..b4ed8cb1e55cbf688528378b840a5613175300d9
Binary files /dev/null and b/sphinx/build/html/_images/current_board.jpg differ
diff --git a/sphinx/build/html/_sources/page1.rst.txt b/sphinx/build/html/_sources/page1.rst.txt
index 78d263b46f67d042b3672e3eb276d4abfed6c7ec..ae502eb9eaf47a7b506777e2d92a0f5708848e50 100644
--- a/sphinx/build/html/_sources/page1.rst.txt
+++ b/sphinx/build/html/_sources/page1.rst.txt
@@ -1,6 +1,6 @@
-**************
-OhmPi V 1.01
-**************
+*****************************************
+OhmPi V 1.01 (limited to 32 electrodes)
+*****************************************
The philosophy of Ohmpi
******************************************
@@ -51,4 +51,25 @@ The measurement board must be printed using the PCB file (Source file repository
Measurement board installation with Raspberry Pi
Current injection
-******************
\ No newline at end of file
+******************
+
+To carry out the electrical resistivity measurement, the first step consists of injecting current into the ground.
+In our case, a simple 12-V lead-acid battery is used to create an electrical potential difference that results
+in current circulating into the ground. The current is injected through electrodes A and B (see Fig. 2). This
+injection is controlled via a 4-channel relay module board connected to the Raspberry Pi. The mechanical relay
+module board is shown in Figure 4. Relays 1 and 2 serve to switch on the current source. The common contacts
+of relays 1 and 2 are connected to the positive and negative battery poles, respectively. The normally open
+contacts of both relays are connected to the common contacts of relays 3 and 4. Relays 1 and 2 are connected
+to the GPIO 7 on the Raspberry Pi and therefore activate simultaneously. The role of relays 3 and 4 is to reverse
+the polarity at electrodes A and B. Thus, when relays 3 and 4 are energized by the GPIO 8 in the open position,
+the positive battery pole is connected to electrode A and the negative pole to electrode B. When not energized,
+they remain in the normally closed position. This set-up offers a simple and robust solution to inject current.
+
+.. figure:: current_board.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Wiring of the 4-channel relay module board for current injection management
\ No newline at end of file
diff --git a/sphinx/build/html/genindex.html b/sphinx/build/html/genindex.html
index 09f24c766bc312d40d5b349aea676b4698de43e3..df8c6b9d0fcc310746f474670b76a4447968f34b 100644
--- a/sphinx/build/html/genindex.html
+++ b/sphinx/build/html/genindex.html
@@ -82,7 +82,7 @@
<ul>
<li class="toctree-l1"><a class="reference internal" href="page0.html"><strong>Introduction to OhmPi</strong></a></li>
-<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01</a></li>
+<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
</ul>
diff --git a/sphinx/build/html/index.html b/sphinx/build/html/index.html
index ea9055d209f01ae8535ff363096907b937225878..118c6056dc89e1d894f977148c756d3901c7ef2e 100644
--- a/sphinx/build/html/index.html
+++ b/sphinx/build/html/index.html
@@ -83,7 +83,7 @@
<ul>
<li class="toctree-l1"><a class="reference internal" href="page0.html"><strong>Introduction to OhmPi</strong></a></li>
-<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01</a></li>
+<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
</ul>
@@ -156,7 +156,7 @@
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="page0.html"><strong>Introduction to OhmPi</strong></a></li>
-<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01</a><ul>
+<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a><ul>
<li class="toctree-l2"><a class="reference internal" href="page1.html#the-philosophy-of-ohmpi">The philosophy of Ohmpi</a></li>
<li class="toctree-l2"><a class="reference internal" href="page1.html#os-installation-on-a-raspberry-pi">OS installation on a Raspberry Pi</a></li>
<li class="toctree-l2"><a class="reference internal" href="page1.html#construction-of-the-measurement-board-and-connection-to-the-raspberry">Construction of the measurement board and connection to the Raspberry</a></li>
diff --git a/sphinx/build/html/objects.inv b/sphinx/build/html/objects.inv
index 54b2cbba771979dab8aadf5b1980d75c5e856a1d..ec68450f1ece6abcf4af11fceead33e4a5bdb5f9 100644
Binary files a/sphinx/build/html/objects.inv and b/sphinx/build/html/objects.inv differ
diff --git a/sphinx/build/html/page1.html b/sphinx/build/html/page1.html
index 3fd3aa06d0895fff7d531aa297ebb79a6199e70b..53fa08feac28cc2c4abc01fab30debc95856dde5 100644
--- a/sphinx/build/html/page1.html
+++ b/sphinx/build/html/page1.html
@@ -7,7 +7,7 @@
<meta name="viewport" content="width=device-width, initial-scale=1.0">
- <title>OhmPi V 1.01 — Ohmpi: open hardware resistivity-meter documentation</title>
+ <title>OhmPi V 1.01 (limited to 32 electrodes) — Ohmpi: open hardware resistivity-meter documentation</title>
@@ -83,7 +83,7 @@
<ul class="current">
<li class="toctree-l1"><a class="reference internal" href="page0.html"><strong>Introduction to OhmPi</strong></a></li>
-<li class="toctree-l1 current"><a class="current reference internal" href="#">OhmPi V 1.01</a><ul>
+<li class="toctree-l1 current"><a class="current reference internal" href="#">OhmPi V 1.01 (limited to 32 electrodes)</a><ul>
<li class="toctree-l2"><a class="reference internal" href="#the-philosophy-of-ohmpi">The philosophy of Ohmpi</a></li>
<li class="toctree-l2"><a class="reference internal" href="#os-installation-on-a-raspberry-pi">OS installation on a Raspberry Pi</a></li>
<li class="toctree-l2"><a class="reference internal" href="#construction-of-the-measurement-board-and-connection-to-the-raspberry">Construction of the measurement board and connection to the Raspberry</a></li>
@@ -136,7 +136,7 @@
<li><a href="index.html" class="icon icon-home"></a> »</li>
- <li>OhmPi V 1.01</li>
+ <li>OhmPi V 1.01 (limited to 32 electrodes)</li>
<li class="wy-breadcrumbs-aside">
@@ -155,8 +155,8 @@
<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
<div itemprop="articleBody">
- <div class="section" id="ohmpi-v-1-01">
-<h1>OhmPi V 1.01<a class="headerlink" href="#ohmpi-v-1-01" title="Permalink to this headline">¶</a></h1>
+ <div class="section" id="ohmpi-v-1-01-limited-to-32-electrodes">
+<h1>OhmPi V 1.01 (limited to 32 electrodes)<a class="headerlink" href="#ohmpi-v-1-01-limited-to-32-electrodes" title="Permalink to this headline">¶</a></h1>
<div class="section" id="the-philosophy-of-ohmpi">
<h2>The philosophy of Ohmpi<a class="headerlink" href="#the-philosophy-of-ohmpi" title="Permalink to this headline">¶</a></h2>
<p>The philosophy of Ohmpi V1.01 is to offer a multi electrode resistivity meter, from a set of commercially available electronic cards it is a resistivity meter limited to 32 electrodes only. It is limited to low-current injection, but suitable for small laboratory experiments and small field time monitoring</p>
@@ -192,6 +192,21 @@ Raspbian GUI settings menu. Failure to carry out this task may cause damage to t
</div>
<div class="section" id="current-injection">
<h2>Current injection<a class="headerlink" href="#current-injection" title="Permalink to this headline">¶</a></h2>
+<p>To carry out the electrical resistivity measurement, the first step consists of injecting current into the ground.
+In our case, a simple 12-V lead-acid battery is used to create an electrical potential difference that results
+in current circulating into the ground. The current is injected through electrodes A and B (see Fig. 2). This
+injection is controlled via a 4-channel relay module board connected to the Raspberry Pi. The mechanical relay
+module board is shown in Figure 4. Relays 1 and 2 serve to switch on the current source. The common contacts
+of relays 1 and 2 are connected to the positive and negative battery poles, respectively. The normally open
+contacts of both relays are connected to the common contacts of relays 3 and 4. Relays 1 and 2 are connected
+to the GPIO 7 on the Raspberry Pi and therefore activate simultaneously. The role of relays 3 and 4 is to reverse
+the polarity at electrodes A and B. Thus, when relays 3 and 4 are energized by the GPIO 8 in the open position,
+the positive battery pole is connected to electrode A and the negative pole to electrode B. When not energized,
+they remain in the normally closed position. This set-up offers a simple and robust solution to inject current.</p>
+<div class="align-center figure" id="id3">
+<a class="reference internal image-reference" href="_images/current_board.jpg"><img alt="alternate text" src="_images/current_board.jpg" style="width: 800px; height: 400px;" /></a>
+<p class="caption"><span class="caption-text">Wiring of the 4-channel relay module board for current injection management</span><a class="headerlink" href="#id3" title="Permalink to this image">¶</a></p>
+</div>
</div>
</div>
diff --git a/sphinx/build/html/search.html b/sphinx/build/html/search.html
index 179e4726775bb03f1822b4bea9e8aca922b8bd85..609593a7bf204fecab6c4347e327d4589cf32db3 100644
--- a/sphinx/build/html/search.html
+++ b/sphinx/build/html/search.html
@@ -84,7 +84,7 @@
<ul>
<li class="toctree-l1"><a class="reference internal" href="page0.html"><strong>Introduction to OhmPi</strong></a></li>
-<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01</a></li>
+<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
</ul>
diff --git a/sphinx/build/html/searchindex.js b/sphinx/build/html/searchindex.js
index e5698d4a2daf58c66b471edfc1edd3be1992bb98..1b47d8ec58a27d60b849524103c19f412e099240 100644
--- a/sphinx/build/html/searchindex.js
+++ b/sphinx/build/html/searchindex.js
@@ -1 +1 @@
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\ No newline at end of file
diff --git a/sphinx/source/current_board.jpg b/sphinx/source/current_board.jpg
new file mode 100644
index 0000000000000000000000000000000000000000..b4ed8cb1e55cbf688528378b840a5613175300d9
Binary files /dev/null and b/sphinx/source/current_board.jpg differ
diff --git a/sphinx/source/page1.rst b/sphinx/source/page1.rst
index c462a98442f43710fcceb56a595dd4cfe55412fd..b297ede2abc2de434cf55445719ab8ee88f9e35b 100644
--- a/sphinx/source/page1.rst
+++ b/sphinx/source/page1.rst
@@ -1,6 +1,6 @@
-**************
+*****************************************
OhmPi V 1.01 (limited to 32 electrodes)
-**************
+*****************************************
The philosophy of Ohmpi
******************************************
@@ -51,4 +51,37 @@ The measurement board must be printed using the PCB file (Source file repository
Measurement board installation with Raspberry Pi
Current injection
-******************
\ No newline at end of file
+******************
+
+To carry out the electrical resistivity measurement, the first step consists of injecting current into the ground.
+In our case, a simple 12-V lead-acid battery is used to create an electrical potential difference that results
+in current circulating into the ground. The current is injected through electrodes A and B (see Fig. 2). This
+injection is controlled via a 4-channel relay module board connected to the Raspberry Pi. The mechanical relay
+module board is shown in Figure 4. Relays 1 and 2 serve to switch on the current source. The common contacts
+of relays 1 and 2 are connected to the positive and negative battery poles, respectively. The normally open
+contacts of both relays are connected to the common contacts of relays 3 and 4. Relays 1 and 2 are connected
+to the GPIO 7 on the Raspberry Pi and therefore activate simultaneously. The role of relays 3 and 4 is to reverse
+the polarity at electrodes A and B. Thus, when relays 3 and 4 are energized by the GPIO 8 in the open position,
+the positive battery pole is connected to electrode A and the negative pole to electrode B. When not energized,
+they remain in the normally closed position. This set-up offers a simple and robust solution to inject current.
+
+.. figure:: current_board.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Wiring of the 4-channel relay module board for current injection management
+
+Electrical resistivity measurements
+************************************
+
+To measure electrical resistivity with Raspberry Pi, an ADS1115 was introduced, as proposed by Florsch [7]. The ADS1115 is a 16-bit ADC (Analog-to-Digital Converter), with an adaptable gain. Its value has been set at 1 in this study. The input signal value could lie between - to + 6.114 V. The ADS1115 is mounted on a board adapted from an in-house design. Figure 5 shows the general diagram for the electronic measurement board developed. This figure also displays the test circuit used to test the board in the laboratory, which mimics the behavior of a soil subjected to current injection. In this test circuit, resistance R11 represents the soil resistance.
+Soil resistance R11 is connected to electrodes A and B for the current injection. Resistors R10 and R12 constitute the contact resistances between soil and electrodes; they are typically made of stainless steel. The battery, which allows for direct current injection, is connected in series with resistors R10, R11 and R12. In this part of the board, resistance R9 has been added to measure the current flowing between electrodes A and B. This resistance value has been set at 50 ohms in order to ensure:
+• a precise resistance,
+• a resistance less than the sum of resistors R10, R11 and R12; indeed, R10 and R12 generally lie between 100 and 5,000 ohms.
+To measure the current intensity between A and B, the electrical potential difference at the pole of the reference resistor (R9) is measured. The intensity (in mA) is calculated by inserting the resulting value into the following: ?
+To measure the potential difference needed to measure current intensity, the ADS 1115 is connected to the ground of the circuit. In our case, the ground reference is electrode B. The analog inputs A1 and A0 of the ADS1115 are connected to each pole of the reference resistor (R9). In order to increase input impedance and adapt the signal gain, tracking amplifiers have been included and completed by a divider bridge (R5, R8, R6 and R7) located between the two amplifiers. The resistance of the divider bridge ensures that the signal remains between 0 and 5 V, in accordance with the ADS1115 signal gain. To measure the potential difference, the M and N electrodes are connected to analog inputs A2 and A3 of the ADS 1115. Between the ADC and the electrodes, two tracking amplifiers and a divider bridge have been positioned so as to obtain a potential lying within the 0-5 V range at the analog input of the ADS 1115.
+Let's note that the potential difference value would equal the potential measured with ADS1115 multiplied by the voltage reduction value of the divider bridge (see Section 5.2). Despite the use of high-resolution resistance (i.e. accurate to within 1%), it is still necessary to calibrate the divider bridge using a precision voltmeter. For this purpose, the input and output potentials of the divider bridge must be measured using an equivalent circuit for various electrical potential values. These values serve to calculate the gain. With this electronic board, it is possible to measure the potential and intensity without disturbing the electric field in the ground, with the total input impedance value being estimated at 36 mega-ohms.
+A shortcut between Electrodes A and B will generate excessive currents, whose intensities depend on the type of battery used. A lithium ion battery or automobile-type lead-acid battery can deliver a strong enough current to damage the board and, as such, constitutes a potential hazard. We therefore recommend adding a 1.5-A fuse between the battery and resistor R9.