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diff --git a/sphinx/build/html/_sources/page0.rst.txt b/sphinx/build/html/_sources/page0.rst.txt
index a392f7a74d349adae804e362c10c3dba182f48dc..dfd7231738bcdb19f0348dfad54778cac841bcae 100644
--- a/sphinx/build/html/_sources/page0.rst.txt
+++ b/sphinx/build/html/_sources/page0.rst.txt
@@ -3,13 +3,26 @@ Premiere page
*************
-
.. image:: logo_ohmpi.JPG
:align: center
+
+Authors:
+
+| Rémi CLEMENT,Vivien DUBOIS,Nicolas Forquet, INRAE, REVERSAAL, F-69626, Villeurbanne Cedex, France.
+| Yannick FARGIER, GERS-RRO, Univ Gustave Eiffel, IFSTTAR, Univ Lyon, F-69675 Lyon, France.
+| Julien GANCE, IRIS Instruments, 45100 Orléans, France.
+| Hélène GUYARD, IGE Grenoble, Université Grenoble Alpes, Grenoble.
+
+Creation date : Juillet 2020.
+
+Update : 18 août 2020.
+
+Status of document: In progress.
**Introduction to OhmPi**
*************************
+
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\
diff --git a/sphinx/build/html/_sources/page1.rst.txt b/sphinx/build/html/_sources/page1.rst.txt
index ac21eeab8c526cef8c3b3f4461315e67ff7cf5de..bcb385ffea4c955f9af0782423db003fb5df4ea9 100644
--- a/sphinx/build/html/_sources/page1.rst.txt
+++ b/sphinx/build/html/_sources/page1.rst.txt
@@ -4,7 +4,9 @@ OhmPi V 1.01 (limited to 32 electrodes)
The philosophy of Ohmpi
******************************************
-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
+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
@@ -21,7 +23,8 @@ Raspbian GUI settings menu. Failure to carry out this task may cause damage to t
Construction of the measurement board and connection to the Raspberry
**************************************************************************
-The measurement board must be printed using the PCB file (Source file repository), with components soldered onto it by following the steps described below and illustrated in the following figure :
+The measurement board must be printed using the PCB file (Source file repository), with components soldered onto
+it by following the steps described below and illustrated in the following figure :
* Step no. 1: installation of the 1-Kohm resistors with an accuracy of ± 1%.
@@ -30,7 +33,11 @@ The measurement board must be printed using the PCB file (Source file repository
* Step no. 4: installation of the 50-Ohm reference resistor ± 0.1%
* Step no. 5: addition of both the ADS115 directly onto the header (pins must be plugged according to the figure) and the LM358N operational amplifiers (pay attention to the direction).
-1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors. Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to place a fuse holder with a 1.5-A fuse for safety purposes.
+1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker
+or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors.
+Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the
+battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to
+place a fuse holder with a 1.5-A fuse for safety purposes.
.. figure:: measurement_board.jpg
:width: 800px
@@ -77,14 +84,37 @@ they remain in the normally closed position. This set-up offers a simple and rob
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:
+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.
+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.
.. figure:: schema_measurement_board.jpg
:width: 800px
@@ -93,4 +123,60 @@ A shortcut between Electrodes A and B will generate excessive currents, whose in
:alt: alternate text
:figclass: align-center
- Measurement board
\ No newline at end of file
+ Measurement board
+
+Multiplexer implentation
+*************************
+The resistivity measurement is conducted on four terminals (A, B, M and N). The user could perform each measurement
+by manually plugging four electrodes into the four channel terminals. In practice, ERT requires several tens or thousands
+of measurements conducted on different electrode arrays. A multiplexer is therefore used to connect each channel to one of
+the 32 electrodes stuck into the ground, all of which are connected to the data logger.
+
+
+We will describe below how to assemble the four multiplexers (MUX), one per terminal. A multiplexer consists of 2 relay
+modules with 16 channels each. On the first board, on each MUX, 15 relays out of the 16 available will be used. Please note that the suggested
+configuration enables making smaller multiplexers (8 or 16 electrodes only). On the other hand, if you prefer upping to 64 electrodes,
+which is entirely possible, a GPIO channel multiplier will have to be used.
+To prepare the multiplexer, the channels of the two relay boards must be connected according to the wiring diagram shown below.
+
+.. figure:: multiplexer_implementation.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Schematic diagram of the wiring of two 16-channel relay shields
+
+
+For this purpose, 0.5-mm² cables with end caps are used and their length adjusted for each connection in order to produce a clean assembly.
+The length was adjusted so that the distance between the two points to be connected could be directly measured on the board once they had
+been assembled one above the other, in adding an extra 3 cm. The wires at the ends need to be stripped and the end caps added.
+As a final step, connect the cables to the correct connectors. This operation must be repeated in order to carry out all the wiring shown in Figure below.
+
+Once the operation has been completed, the 16 control pins of each 16-channel relay shield card must be prepared. Each card actually contains 16 input channels
+for activating each relay (Fig. 12). However, we will be activating several relays with a single GPIO (to limit the number of GPIOs used on Raspberry Pi,
+see Section 2.4). To execute this step, it will be necessary to follow the protocol presented in Figure.
+
+ .. figure:: connection.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Connection to the 16-channel relay shield
+
+For the 16-channel relay shield no. 1, these steps must be followed:
+* Position a test circuit with 10 horizontal and 10 vertical holes on the pins of the 16-channel relay shield board.
+* Follow the diagram and solder the pins as shown in Fig.
+* Lastly, solder 0.5-mm² wires 1 m in length to the test circuit.
+
+For relay shield no. 2, follow the same procedure, but solder all the pins together (d-e-f).
+This same operation must be repeated for the other three multiplexers as well.
+The next step consists of connecting the relay card inputs to the Raspberry Pi according to Table 5 for all four multiplexers.
+
+
+
+
+
\ No newline at end of file
diff --git a/sphinx/build/html/index.html b/sphinx/build/html/index.html
index a2abd7c461b67bdd0adb9ed54a371177ee22d715..8a9569cbe4708b1c0e4dcf69140da7ef79951d04 100644
--- a/sphinx/build/html/index.html
+++ b/sphinx/build/html/index.html
@@ -162,6 +162,7 @@
<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>
<li class="toctree-l2"><a class="reference internal" href="page1.html#current-injection">Current injection</a></li>
<li class="toctree-l2"><a class="reference internal" href="page1.html#electrical-resistivity-measurements">Electrical resistivity measurements</a></li>
+<li class="toctree-l2"><a class="reference internal" href="page1.html#multiplexer-implentation">Multiplexer implentation</a></li>
</ul>
</li>
</ul>
diff --git a/sphinx/build/html/page0.html b/sphinx/build/html/page0.html
index 0d6f9a5e43b0b2e80c349ab88f2eddae8dec8ed1..03d6a41dabdc48bdab5bb957e73171449c667f03 100644
--- a/sphinx/build/html/page0.html
+++ b/sphinx/build/html/page0.html
@@ -36,7 +36,7 @@
<link rel="index" title="Index" href="genindex.html" />
<link rel="search" title="Search" href="search.html" />
- <link rel="next" title="OhmPi V 1.01" href="page1.html" />
+ <link rel="next" title="OhmPi V 1.01 (limited to 32 electrodes)" href="page1.html" />
<link rel="prev" title="OHMPI: Open source and open hardware resitivity-meter" href="index.html" />
</head>
@@ -84,7 +84,7 @@
<ul class="current">
<li class="toctree-l1 current"><a class="current reference internal" href="#"><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>
@@ -151,6 +151,16 @@
<div itemprop="articleBody">
<img alt="_images/logo_ohmpi.JPG" class="align-center" src="_images/logo_ohmpi.JPG" />
+<p>Authors:</p>
+<div class="line-block">
+<div class="line">Rémi CLEMENT,Vivien DUBOIS,Nicolas Forquet, INRAE, REVERSAAL, F-69626, Villeurbanne Cedex, France.</div>
+<div class="line">Yannick FARGIER, GERS-RRO, Univ Gustave Eiffel, IFSTTAR, Univ Lyon, F-69675 Lyon, France.</div>
+<div class="line">Julien GANCE, IRIS Instruments, 45100 Orléans, France.</div>
+<div class="line">Hélène GUYARD, IGE Grenoble, Université Grenoble Alpes, Grenoble.</div>
+</div>
+<p>Creation date : Juillet 2020.</p>
+<p>Update : 18 août 2020.</p>
+<p>Status of document: In progress.</p>
<div class="section" id="introduction-to-ohmpi">
<h1><strong>Introduction to OhmPi</strong><a class="headerlink" href="#introduction-to-ohmpi" title="Permalink to this headline">¶</a></h1>
<p>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 meterfeatures current injection and measurement functions associated with a multiplexer that allows performing automatic measurements with up to 32 electrodes.OhmPi’s philosophy is to provide a fully open source and open hardware tool /
@@ -169,7 +179,7 @@ to the near surface scientific community.</p>
<div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
- <a href="page1.html" class="btn btn-neutral float-right" title="OhmPi V 1.01" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a>
+ <a href="page1.html" class="btn btn-neutral float-right" title="OhmPi V 1.01 (limited to 32 electrodes)" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a>
<a href="index.html" class="btn btn-neutral float-left" title="OHMPI: Open source and open hardware resitivity-meter" accesskey="p" rel="prev"><span class="fa fa-arrow-circle-left"></span> Previous</a>
diff --git a/sphinx/build/html/page1.html b/sphinx/build/html/page1.html
index 9c667573fba83f18f8fecf1e7b694aff3bd5af08..6c3c11a3842c1237617229a53437588a5245bddd 100644
--- a/sphinx/build/html/page1.html
+++ b/sphinx/build/html/page1.html
@@ -89,6 +89,7 @@
<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>
<li class="toctree-l2"><a class="reference internal" href="#current-injection">Current injection</a></li>
<li class="toctree-l2"><a class="reference internal" href="#electrical-resistivity-measurements">Electrical resistivity measurements</a></li>
+<li class="toctree-l2"><a class="reference internal" href="#multiplexer-implentation">Multiplexer implentation</a></li>
</ul>
</li>
</ul>
@@ -160,7 +161,9 @@
<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>
+<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>
</div>
<div class="section" id="os-installation-on-a-raspberry-pi">
<h2>OS installation on a Raspberry Pi<a class="headerlink" href="#os-installation-on-a-raspberry-pi" title="Permalink to this headline">¶</a></h2>
@@ -173,7 +176,8 @@ Raspbian GUI settings menu. Failure to carry out this task may cause damage to t
</div>
<div class="section" id="construction-of-the-measurement-board-and-connection-to-the-raspberry">
<h2>Construction of the measurement board and connection to the Raspberry<a class="headerlink" href="#construction-of-the-measurement-board-and-connection-to-the-raspberry" title="Permalink to this headline">¶</a></h2>
-<p>The measurement board must be printed using the PCB file (Source file repository), with components soldered onto it by following the steps described below and illustrated in the following figure :</p>
+<p>The measurement board must be printed using the PCB file (Source file repository), with components soldered onto
+it by following the steps described below and illustrated in the following figure :</p>
<ul class="simple">
<li><p>Step no. 1: installation of the 1-Kohm resistors with an accuracy of ± 1%.</p></li>
<li><p>Step no. 2: installation of the 1.5-Kohm resistors with an accuracy of ± 1%.</p></li>
@@ -181,7 +185,11 @@ Raspbian GUI settings menu. Failure to carry out this task may cause damage to t
<li><p>Step no. 4: installation of the 50-Ohm reference resistor ± 0.1%</p></li>
<li><p>Step no. 5: addition of both the ADS115 directly onto the header (pins must be plugged according to the figure) and the LM358N operational amplifiers (pay attention to the direction).</p></li>
</ul>
-<p>1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors. Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to place a fuse holder with a 1.5-A fuse for safety purposes.</p>
+<p>1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker
+or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors.
+Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the
+battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to
+place a fuse holder with a 1.5-A fuse for safety purposes.</p>
<div class="align-center figure" id="id1">
<a class="reference internal image-reference" href="_images/measurement_board.jpg"><img alt="alternate text" src="_images/measurement_board.jpg" style="width: 800px; height: 400px;" /></a>
<p class="caption"><span class="caption-text">Measurement circuit board assembly: a) printed circuit board, b) adding the 1-Kohm resistors ± 1%, c)adding the 1.5-Kohm resistors ± 1%, d) adding the black female 1 x 10 header and the 7-blue screw terminal block(2 pin, 3.5-mm pitch), e) adding the 50-ohm reference resistor ± 0.1%, and f) adding the ADS1115 and the LM358N low-power dual operational amplifiers</span><a class="headerlink" href="#id1" title="Permalink to this image">¶</a></p>
@@ -211,19 +219,78 @@ they remain in the normally closed position. This set-up offers a simple and rob
</div>
<div class="section" id="electrical-resistivity-measurements">
<h2>Electrical resistivity measurements<a class="headerlink" href="#electrical-resistivity-measurements" title="Permalink to this headline">¶</a></h2>
-<p>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:
+<p>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.</p>
+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.</p>
<div class="align-center figure" id="id4">
<a class="reference internal image-reference" href="_images/schema_measurement_board.jpg"><img alt="alternate text" src="_images/schema_measurement_board.jpg" style="width: 800px; height: 400px;" /></a>
<p class="caption"><span class="caption-text">Measurement board</span><a class="headerlink" href="#id4" title="Permalink to this image">¶</a></p>
</div>
</div>
+<div class="section" id="multiplexer-implentation">
+<h2>Multiplexer implentation<a class="headerlink" href="#multiplexer-implentation" title="Permalink to this headline">¶</a></h2>
+<p>The resistivity measurement is conducted on four terminals (A, B, M and N). The user could perform each measurement
+by manually plugging four electrodes into the four channel terminals. In practice, ERT requires several tens or thousands
+of measurements conducted on different electrode arrays. A multiplexer is therefore used to connect each channel to one of
+the 32 electrodes stuck into the ground, all of which are connected to the data logger.</p>
+<p>We will describe below how to assemble the four multiplexers (MUX), one per terminal. A multiplexer consists of 2 relay
+modules with 16 channels each. On the first board, on each MUX, 15 relays out of the 16 available will be used. Please note that the suggested
+configuration enables making smaller multiplexers (8 or 16 electrodes only). On the other hand, if you prefer upping to 64 electrodes,
+which is entirely possible, a GPIO channel multiplier will have to be used.
+To prepare the multiplexer, the channels of the two relay boards must be connected according to the wiring diagram shown below.</p>
+<div class="align-center figure" id="id5">
+<a class="reference internal image-reference" href="_images/multiplexer_implementation.jpg"><img alt="alternate text" src="_images/multiplexer_implementation.jpg" style="width: 800px; height: 400px;" /></a>
+<p class="caption"><span class="caption-text">Schematic diagram of the wiring of two 16-channel relay shields</span><a class="headerlink" href="#id5" title="Permalink to this image">¶</a></p>
+</div>
+<p>For this purpose, 0.5-mm² cables with end caps are used and their length adjusted for each connection in order to produce a clean assembly.
+The length was adjusted so that the distance between the two points to be connected could be directly measured on the board once they had
+been assembled one above the other, in adding an extra 3 cm. The wires at the ends need to be stripped and the end caps added.
+As a final step, connect the cables to the correct connectors. This operation must be repeated in order to carry out all the wiring shown in Figure below.</p>
+<p>Once the operation has been completed, the 16 control pins of each 16-channel relay shield card must be prepared. Each card actually contains 16 input channels
+for activating each relay (Fig. 12). However, we will be activating several relays with a single GPIO (to limit the number of GPIOs used on Raspberry Pi,
+see Section 2.4). To execute this step, it will be necessary to follow the protocol presented in Figure.</p>
+<blockquote>
+<div><div class="align-center figure" id="id6">
+<a class="reference internal image-reference" href="_images/connection.jpg"><img alt="alternate text" src="_images/connection.jpg" style="width: 800px; height: 400px;" /></a>
+<p class="caption"><span class="caption-text">Connection to the 16-channel relay shield</span><a class="headerlink" href="#id6" title="Permalink to this image">¶</a></p>
+</div>
+</div></blockquote>
+<p>For the 16-channel relay shield no. 1, these steps must be followed:
+* Position a test circuit with 10 horizontal and 10 vertical holes on the pins of the 16-channel relay shield board.
+* Follow the diagram and solder the pins as shown in Fig.
+* Lastly, solder 0.5-mm² wires 1 m in length to the test circuit.</p>
+<p>For relay shield no. 2, follow the same procedure, but solder all the pins together (d-e-f).
+This same operation must be repeated for the other three multiplexers as well.
+The next step consists of connecting the relay card inputs to the Raspberry Pi according to Table 5 for all four multiplexers.</p>
+</div>
</div>
diff --git a/sphinx/build/html/searchindex.js b/sphinx/build/html/searchindex.js
index 9bf84355b567bbb00eb283365cb2e5376d77b1a9..362342c2573cfef88f5671896907f5dc74a47d2d 100644
--- a/sphinx/build/html/searchindex.js
+++ b/sphinx/build/html/searchindex.js
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diff --git a/sphinx/source/connection.jpg b/sphinx/source/connection.jpg
new file mode 100644
index 0000000000000000000000000000000000000000..e2b5e01b748d01d8eeed57b2526b83dd00822605
Binary files /dev/null and b/sphinx/source/connection.jpg differ
diff --git a/sphinx/source/multiplexer_implementation.jpg b/sphinx/source/multiplexer_implementation.jpg
new file mode 100644
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diff --git a/sphinx/source/page0.rst b/sphinx/source/page0.rst
index a392f7a74d349adae804e362c10c3dba182f48dc..dfd7231738bcdb19f0348dfad54778cac841bcae 100644
--- a/sphinx/source/page0.rst
+++ b/sphinx/source/page0.rst
@@ -3,13 +3,26 @@ Premiere page
*************
-
.. image:: logo_ohmpi.JPG
:align: center
+
+Authors:
+
+| Rémi CLEMENT,Vivien DUBOIS,Nicolas Forquet, INRAE, REVERSAAL, F-69626, Villeurbanne Cedex, France.
+| Yannick FARGIER, GERS-RRO, Univ Gustave Eiffel, IFSTTAR, Univ Lyon, F-69675 Lyon, France.
+| Julien GANCE, IRIS Instruments, 45100 Orléans, France.
+| Hélène GUYARD, IGE Grenoble, Université Grenoble Alpes, Grenoble.
+
+Creation date : Juillet 2020.
+
+Update : 18 août 2020.
+
+Status of document: In progress.
**Introduction to OhmPi**
*************************
+
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\
diff --git a/sphinx/source/page1.rst b/sphinx/source/page1.rst
index f693b375cd9ff18e7a59ef3725334c6d7752d4e5..7b283aaeeead45343471bed24815f848848ba596 100644
--- a/sphinx/source/page1.rst
+++ b/sphinx/source/page1.rst
@@ -4,8 +4,9 @@ OhmPi V 1.01 (limited to 32 electrodes)
The philosophy of Ohmpi
******************************************
-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
-
+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
OS installation on a Raspberry Pi
@@ -21,7 +22,8 @@ Raspbian GUI settings menu. Failure to carry out this task may cause damage to t
Construction of the measurement board and connection to the Raspberry
**************************************************************************
-The measurement board must be printed using the PCB file (Source file repository), with components soldered onto it by following the steps described below and illustrated in the following figure :
+The measurement board must be printed using the PCB file (Source file repository), with components soldered onto
+it by following the steps described below and illustrated in the following figure :
* Step no. 1: installation of the 1-Kohm resistors with an accuracy of ± 1%.
@@ -30,7 +32,11 @@ The measurement board must be printed using the PCB file (Source file repository
* Step no. 4: installation of the 50-Ohm reference resistor ± 0.1%
* Step no. 5: addition of both the ADS115 directly onto the header (pins must be plugged according to the figure) and the LM358N operational amplifiers (pay attention to the direction).
-1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors. Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to place a fuse holder with a 1.5-A fuse for safety purposes.
+1-Kohm and 1.5-Kohm resistors apply to the divider bridge. If, for example, you prefer using a weaker
+or stronger power supply, it would be possible to adjust the divider bridge value by simply modifying these resistors.
+Once all the components have been soldered together, the measurement board can be connected to the Raspberry Pi and the
+battery terminal, according to Figure 9. Between the battery and the TX+ terminal of the measurement board, remember to
+place a fuse holder with a 1.5-A fuse for safety purposes.
.. figure:: measurement_board.jpg
:width: 800px
@@ -77,14 +83,37 @@ they remain in the normally closed position. This set-up offers a simple and rob
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:
+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.
+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.
.. figure:: schema_measurement_board.jpg
:width: 800px
@@ -103,7 +132,50 @@ of measurements conducted on different electrode arrays. A multiplexer is theref
the 32 electrodes stuck into the ground, all of which are connected to the data logger.
-We will describe below how to assemble the four multiplexers (MUX), one per terminal.
-A multiplexer consists of 2 relay modules with 16 channels each. On the first board, on each MUX, 15 relays out of the 16 available will be used. Please note that the suggested configuration enables making smaller multiplexers (8 or 16 electrodes only). On the other hand, if you prefer upping to 64 electrodes, which is entirely possible, a GPIO channel multiplier will have to be used. To prepare the multiplexer, the channels of the two relay boards must be connected according to the wiring diagram shown in Figure 11. For this purpose, 0.5-mm² cables with end caps are used and their length adjusted for each connection in order to produce a clean assembly. The length was adjusted so that the distance between the two points to be connected could be directly measured on the board once they had been assembled one above the other, in adding an extra 3 cm. The wires at the ends need to be stripped and the end caps added. As a final step, connect the cables to the correct connectors. This operation must be repeated in order to carry out all the wiring shown in Figure 11.
+We will describe below how to assemble the four multiplexers (MUX), one per terminal. A multiplexer consists of 2 relay
+modules with 16 channels each. On the first board, on each MUX, 15 relays out of the 16 available will be used. Please note that the suggested
+configuration enables making smaller multiplexers (8 or 16 electrodes only). On the other hand, if you prefer upping to 64 electrodes,
+which is entirely possible, a GPIO channel multiplier will have to be used.
+To prepare the multiplexer, the channels of the two relay boards must be connected according to the wiring diagram shown below.
+
+.. figure:: multiplexer_implementation.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Schematic diagram of the wiring of two 16-channel relay shields
+
+
+For this purpose, 0.5-mm² cables with end caps are used and their length adjusted for each connection in order to produce a clean assembly.
+The length was adjusted so that the distance between the two points to be connected could be directly measured on the board once they had
+been assembled one above the other, in adding an extra 3 cm. The wires at the ends need to be stripped and the end caps added.
+As a final step, connect the cables to the correct connectors. This operation must be repeated in order to carry out all the wiring shown in Figure below.
+
+Once the operation has been completed, the 16 control pins of each 16-channel relay shield card must be prepared. Each card actually contains 16 input channels
+for activating each relay (Fig. 12). However, we will be activating several relays with a single GPIO (to limit the number of GPIOs used on Raspberry Pi,
+see Section 2.4). To execute this step, it will be necessary to follow the protocol presented in Figure.
+
+ .. figure:: connection.jpg
+ :width: 800px
+ :align: center
+ :height: 400px
+ :alt: alternate text
+ :figclass: align-center
+
+ Connection to the 16-channel relay shield
+
+For the 16-channel relay shield no. 1, these steps must be followed:
+* Position a test circuit with 10 horizontal and 10 vertical holes on the pins of the 16-channel relay shield board.
+* Follow the diagram and solder the pins as shown in Fig.
+* Lastly, solder 0.5-mm² wires 1 m in length to the test circuit.
+
+For relay shield no. 2, follow the same procedure, but solder all the pins together (d-e-f).
+This same operation must be repeated for the other three multiplexers as well.
+The next step consists of connecting the relay card inputs to the Raspberry Pi according to Table 5 for all four multiplexers.
+
+
+
\ No newline at end of file