update documentation ohmpi v1

public/_sources/page0.rst.txt

 ************ 
 Premiere page 
 ************* 
-
+**OhmPi project** 
+************************* 
  
-
 .. image:: logo_ohmpi.JPG
+   :width: 350 px
    :align: center
+   :height: 250 px
+   :alt: Logo OhmPi
+  
+
+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.
+
+Parteners:
+
+.. table::
+   :align: center
+  
+   +-------------------------------+-----------------------------------+-------------------------------+-----------------------------------+
+   |   .. image:: logo_inrae.jpg   |  .. image:: logo_univ_gustave.png |   .. image:: logo-iris.jpg    |  .. image:: ige.png               | 
+   +-------------------------------+-----------------------------------+-------------------------------+-----------------------------------+
+   
+
+
+Creation date : Juillet 2020.
+
+Update : 21 août 2020.
+
+Status of document: In progress.
+
    
 **Introduction to OhmPi** 
 ************************* 
 
-This article presents the development of a low-cost, open hardware \ 
+
+This documentation 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.\ 
 OhmPi's philosophy is to provide a fully open source and open hardware tool /
-to the near surface scientific community. 
+to the near surface scientific community.
+
+ 
 
 .. note:: 
    Everyone willing to get involved is  welcome in ohmPi Project!.
\ No newline at end of file

public/_sources/page1.rst.txt

@@ -3,10 +3,38 @@ 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
+
+
+Technical data
+***************
++-------------------------------+--------------------+-----------+
+| **Parameter**                 | **Specifications** | Units     |
++-------------------------------+--------------------+-----------+
+|Electrodes                     |32                  |           |
++-------------------------------+--------------------+-----------+
+|Operating temperature          |0 to 50             |°c         |
++-------------------------------+--------------------+-----------+
+|Power consumption of CPU and   |18.5                |W          |             
+|control system                 |                    |           |
++-------------------------------+--------------------+-----------+
+|Voltage injection              |12                  |V          |
++-------------------------------+--------------------+-----------+
+|Battery                        |12                  |V          |
++-------------------------------+--------------------+-----------+
+|Current                        |0 to 50             |mA         |
++-------------------------------+--------------------+-----------+
+|Min pulse duration             |150                 |mS         |
++-------------------------------+--------------------+-----------+
+|Input impedance                |36                  |Mohm       |
++-------------------------------+--------------------+-----------+
+|Data storage                   |micro SD card       |           |
++-------------------------------+--------------------+-----------+
+|Resolution                     |O.O1                |ohm        |
++-------------------------------+--------------------+-----------+
 
 OS installation on a Raspberry Pi 
 ****************************************** 
@@ -19,9 +47,60 @@ Once the OS has been installed, the 1-wire option and GPIO remote option must be
 Raspbian GUI settings menu. Failure to carry out this task may cause damage to the relay shield cards during measurements.
 
 
+
+
 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 :
+
+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.
+
+.. figure:: schema_measurement_board.jpg
+   :width: 800px
+   :align: center
+   :height: 400px
+   :alt: alternate text
+   :figclass: align-center
+   
+   Measurement board
+
+Implementation
+==============
+
+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 +109,11 @@ 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
@@ -74,23 +157,60 @@ they remain in the normally closed position. This set-up offers a simple and rob
    
    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.
+   
+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.
 
-.. figure:: schema_measurement_board.jpg
+
+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
    
-   Measurement board
\ No newline at end of file
+   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

public/genindex.html

@@ -81,7 +81,8 @@
             
             
               <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="page0.html"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page0.html#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
 <li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
 </ul>
 

public/index.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="Introduction to OhmPi" href="page0.html" /> 
+    <link rel="next" title="OhmPi project" href="page0.html" /> 
 </head>
 
 <body class="wy-body-for-nav">
@@ -82,7 +82,8 @@
             
             
               <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="page0.html"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page0.html#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
 <li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
 </ul>
 
@@ -155,13 +156,15 @@
 <p>Contents:</p>
 <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="page0.html"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page0.html#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
 <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#technical-data">Technical data</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>
 <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>
@@ -183,7 +186,7 @@
   
     <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
       
-        <a href="page0.html" class="btn btn-neutral float-right" title="Introduction to OhmPi" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a>
+        <a href="page0.html" class="btn btn-neutral float-right" title="OhmPi project" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a>
       
       
     </div>

public/page0.html

@@ -7,7 +7,7 @@
   
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   
-  <title>Introduction to OhmPi &mdash; Ohmpi: open hardware resistivity-meter documentation</title>
+  <title>OhmPi project &mdash; Ohmpi: open hardware resistivity-meter documentation</title>
   
 
   
@@ -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>
 
@@ -83,8 +83,9 @@
             
             
               <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 current"><a class="current reference internal" href="#"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
 </ul>
 
             
@@ -131,7 +132,7 @@
     
       <li><a href="index.html" class="icon icon-home"></a> &raquo;</li>
         
-      <li><strong>Introduction to OhmPi</strong></li>
+      <li><strong>OhmPi project</strong></li>
     
     
       <li class="wy-breadcrumbs-aside">
@@ -150,10 +151,43 @@
           <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
            <div itemprop="articleBody">
             
-  <img alt="_images/logo_ohmpi.JPG" class="align-center" src="_images/logo_ohmpi.JPG" />
+  <div class="section" id="ohmpi-project">
+<h1><strong>OhmPi project</strong><a class="headerlink" href="#ohmpi-project" title="Permalink to this headline">¶</a></h1>
+<a class="reference internal image-reference" href="_images/logo_ohmpi.JPG"><img alt="Logo OhmPi" class="align-center" src="_images/logo_ohmpi.JPG" style="width: 350px; height: 250px;" /></a>
+<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>Parteners:</p>
+<table class="docutils align-center">
+<colgroup>
+<col style="width: 23%" />
+<col style="width: 27%" />
+<col style="width: 23%" />
+<col style="width: 27%" />
+</colgroup>
+<tbody>
+<tr class="row-odd"><td><img alt="_images/logo_inrae.jpg" src="_images/logo_inrae.jpg" />
+</td>
+<td><img alt="_images/logo_univ_gustave.png" src="_images/logo_univ_gustave.png" />
+</td>
+<td><img alt="_images/logo-iris.jpg" src="_images/logo-iris.jpg" />
+</td>
+<td><img alt="_images/ige.png" src="_images/ige.png" />
+</td>
+</tr>
+</tbody>
+</table>
+<p>Creation date : Juillet 2020.</p>
+<p>Update : 21 août 2020.</p>
+<p>Status of document: In progress.</p>
+</div>
 <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 /
+<p>This documentation 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 /
 to the near surface scientific community.</p>
 <div class="admonition note">
 <p class="admonition-title">Note</p>
@@ -169,7 +203,7 @@ 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>

public/page1.html

@@ -36,7 +36,7 @@
     
     <link rel="index" title="Index" href="genindex.html" />
     <link rel="search" title="Search" href="search.html" />
-    <link rel="prev" title="Introduction to OhmPi" href="page0.html" /> 
+    <link rel="prev" title="OhmPi project" href="page0.html" /> 
 </head>
 
 <body class="wy-body-for-nav">
@@ -82,13 +82,19 @@
             
             
               <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"><a class="reference internal" href="page0.html"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page0.html#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
 <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="#technical-data">Technical data</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>
+<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><ul>
+<li class="toctree-l3"><a class="reference internal" href="#electrical-resistivity-measurements">Electrical resistivity measurements</a></li>
+<li class="toctree-l3"><a class="reference internal" href="#implementation">Implementation</a></li>
+</ul>
+</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 +166,66 @@
 <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="technical-data">
+<h2>Technical data<a class="headerlink" href="#technical-data" title="Permalink to this headline">¶</a></h2>
+<table class="docutils align-default">
+<colgroup>
+<col style="width: 50%" />
+<col style="width: 32%" />
+<col style="width: 18%" />
+</colgroup>
+<tbody>
+<tr class="row-odd"><td><p><strong>Parameter</strong></p></td>
+<td><p><strong>Specifications</strong></p></td>
+<td><p>Units</p></td>
+</tr>
+<tr class="row-even"><td><p>Electrodes</p></td>
+<td><p>32</p></td>
+<td></td>
+</tr>
+<tr class="row-odd"><td><p>Operating temperature</p></td>
+<td><p>0 to 50</p></td>
+<td><p>°c</p></td>
+</tr>
+<tr class="row-even"><td><p>Power consumption of CPU and
+control system</p></td>
+<td><p>18.5</p></td>
+<td><p>W</p></td>
+</tr>
+<tr class="row-odd"><td><p>Voltage injection</p></td>
+<td><p>12</p></td>
+<td><p>V</p></td>
+</tr>
+<tr class="row-even"><td><p>Battery</p></td>
+<td><p>12</p></td>
+<td><p>V</p></td>
+</tr>
+<tr class="row-odd"><td><p>Current</p></td>
+<td><p>0 to 50</p></td>
+<td><p>mA</p></td>
+</tr>
+<tr class="row-even"><td><p>Min pulse duration</p></td>
+<td><p>150</p></td>
+<td><p>mS</p></td>
+</tr>
+<tr class="row-odd"><td><p>Input impedance</p></td>
+<td><p>36</p></td>
+<td><p>Mohm</p></td>
+</tr>
+<tr class="row-even"><td><p>Data storage</p></td>
+<td><p>micro SD card</p></td>
+<td></td>
+</tr>
+<tr class="row-odd"><td><p>Resolution</p></td>
+<td><p>O.O1</p></td>
+<td><p>ohm</p></td>
+</tr>
+</tbody>
+</table>
 </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 +238,48 @@ 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>
+<div class="section" id="electrical-resistivity-measurements">
+<h3>Electrical resistivity measurements<a class="headerlink" href="#electrical-resistivity-measurements" title="Permalink to this headline">¶</a></h3>
+<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>
+<div class="align-center figure" id="id1">
+<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="#id1" title="Permalink to this image">¶</a></p>
+</div>
+</div>
+<div class="section" id="implementation">
+<h3>Implementation<a class="headerlink" href="#implementation" title="Permalink to this headline">¶</a></h3>
+<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>
@@ -181,14 +287,19 @@ 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>
-<div class="align-center figure" id="id1">
+<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="id2">
 <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>
+<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="#id2" title="Permalink to this image">¶</a></p>
 </div>
-<div class="align-center figure" id="id2">
+<div class="align-center figure" id="id3">
 <a class="reference internal image-reference" href="_images/measurement_board-2.jpg"><img alt="alternate text" src="_images/measurement_board-2.jpg" style="width: 800px; height: 700px;" /></a>
-<p class="caption"><span class="caption-text">Measurement board installation with Raspberry Pi</span><a class="headerlink" href="#id2" title="Permalink to this image">¶</a></p>
+<p class="caption"><span class="caption-text">Measurement board installation with Raspberry Pi</span><a class="headerlink" href="#id3" title="Permalink to this image">¶</a></p>
+</div>
 </div>
 </div>
 <div class="section" id="current-injection">
@@ -204,25 +315,46 @@ to the GPIO 7 on the Raspberry Pi and therefore activate simultaneously. The rol
 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">
+<div class="align-center figure" id="id4">
 <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>
+<p class="caption"><span class="caption-text">Wiring of the 4-channel relay module board for current injection management</span><a class="headerlink" href="#id4" title="Permalink to this image">¶</a></p>
 </div>
 </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:
-•       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>
-<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 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>
 
@@ -235,7 +367,7 @@ A shortcut between Electrodes A and B will generate excessive currents, whose in
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@@ -83,7 +83,8 @@
             
             
               <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="page0.html"><strong>OhmPi project</strong></a></li>
+<li class="toctree-l1"><a class="reference internal" href="page0.html#introduction-to-ohmpi"><strong>Introduction to OhmPi</strong></a></li>
 <li class="toctree-l1"><a class="reference internal" href="page1.html">OhmPi V 1.01 (limited to 32 electrodes)</a></li>
 </ul>
 

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