inconsistent Results

This topic has 8 replies, 3 voices, and was last updated 2017-04-30 at 5:09 PM by lilcano.

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2017-04-23 at 2:21 PM #2164
lilcano
Participant
Hello,
so i am using the SDI-12 library at https://github.com/EnviroDIY/Arduino-SDI-12.git to collect Ea and VWC data from the decagon 5TM sensors attached to an arduino Uno R3. Using the attached sketch, unfortunately the results obtained are inconsistent after several days of data collections. as shown in the plot of the different data points. has any one observed similar results? Or what am i doing wrong in the sketch? Please help
Attachments:
1. plot-of-results.pptx
2017-04-24 at 11:45 AM #2169
Shannon Hicks
Moderator
It would be helpful for you to attach a jpg of png image of your graph instead of a Powerpoint slide. You also can’t attach the raw .ino file to forum posts, but you can cut and paste it using the “code” tags in the post editor tools.

And on your graph, can you please label both the x and y-axis? I don’t know what parameter you’re graphing and on what time scale your measurements covered. I’m assuming your graph shows either temperature or soil moisture. How were you testing the sensor? Was is installed outside or in a controlled environment? What kind of results were you expecting and what makes you think something is inconsistent?

2017-04-25 at 1:36 AM #2172

Participant

Hello,
Thanks for the quick response.Bellow is the sketch running on the arduino Uno R3. The devices where actually tested on the field(not in a controlled environment).The results shown on the plot is VMC collected every minute from the sensors. Actually the VWC is expected to reduce with time, these results are collected over a period of 3 days. Surprisingly they show a sinusoidal curve and the sensors are places in a sandy loam soil. I am thinking maybe the sketch has some problem. Please do you have any ideas why such results?

//This is the first code for taking data from the 5TM sensor and showing it on the Arduino serial mornitor 
#include <SDI12.h>

#define DATAPIN 7         // change to the proper pin for sdi-12 data pin, I prefer D7
SDI12 mySDI12(DATAPIN); 

unsigned long previousMillis = 0;        
const long interval = 60000;        //set the interval (in milliseconds).  ex: 60000 = 60 seconds

void setup () 
{
     pinMode(13, OUTPUT);
     digitalWrite(13, LOW);    //turn off the onboard LED to start with
     Serial.begin(57600);
     mySDI12.begin(); 
     Serial.println("Sketch for sampling multiple SDI12 sensors");
     delay(1000); 
}

void loop () 
{ 
    unsigned long currentMillis = millis(); 
 
    if(currentMillis - previousMillis >= interval || previousMillis == 0) {
   
       previousMillis = currentMillis;   
       digitalWrite(13, HIGH);     //turn on the onboard LED to show that samples are being taken
       Serial.print("Time: ");
       Serial.print(currentMillis/1000);  //print out the current time, in seconds
       Serial.print(" ---- ");
       
       for (char j = '1'; j <= '2'; j++)  {        //go through channels 1 to 6 
         tmMeasurement(j);
         }
       
       Serial.println(); 
       digitalWrite(13, LOW);     //turn off the LED to show that samples are done
     }
     
     delay(1000);
     
} 

void tmMeasurement(char c){        //5TM soil moisture sensor
  String command = ""; 
  float Ea = 0.0;
  float  temp = 0.0;
  float VWC = 0.0;
  command += c;
  command += "M!"; // SDI-12 measurement command format  [address]['M'][!]
  mySDI12.sendCommand(command); 
  delay(500); // wait a sec
  mySDI12.flush();

  command = "";
  command += c;
  command += "D0!"; // SDI-12 command to get data [address][D][dataOption][!]
  mySDI12.sendCommand(command);
  delay(500); 
  
    if(mySDI12.available() > 0){
        int channel = mySDI12.parseInt();
        Ea = mySDI12.parseFloat();
        temp = mySDI12.parseFloat();

      VWC = (4.3e-6*(Ea*Ea*Ea)) - (5.5e-4*(Ea*Ea)) + (2.92e-2 * Ea) - 5.3e-2 ;     //the TOPP equation used to calculate VWC
      
      Serial.print("Sensor:");
      Serial.print(channel);
      Serial.print(": Ea=");
      Serial.print(Ea);             //apparent dielectric permittivity
      Serial.print(", VWC=");
      Serial.print(VWC);            //volumetric water content 
      Serial.print("%, Temp=");
      Serial.print(temp);           //Tempeerature 
      Serial.print("degC  ....  ");
      
   } 
  mySDI12.flush(); 
}

//This is the first code for taking data from the 5TM sensor and showing it on the Arduino serial mornitor

#include <SDI12.h>

#define DATAPIN 7 // change to the proper pin for sdi-12 data pin, I prefer D7

SDI12 mySDI12(DATAPIN);

unsigned long previousMillis = 0;

const long interval = 60000; //set the interval (in milliseconds). ex: 60000 = 60 seconds

void setup ()

{

pinMode(13, OUTPUT);

digitalWrite(13, LOW); //turn off the onboard LED to start with

Serial.begin(57600);

mySDI12.begin();

Serial.println("Sketch for sampling multiple SDI12 sensors");

delay(1000);

}

void loop ()

{

unsigned long currentMillis = millis();

if(currentMillis - previousMillis >= interval || previousMillis == 0) {

previousMillis = currentMillis;

digitalWrite(13, HIGH); //turn on the onboard LED to show that samples are being taken

Serial.print("Time: ");

Serial.print(currentMillis/1000); //print out the current time, in seconds

Serial.print(" ---- ");

for (char j = '1'; j <= '2'; j++) { //go through channels 1 to 6

tmMeasurement(j);

}

Serial.println();

digitalWrite(13, LOW); //turn off the LED to show that samples are done

}

delay(1000);

}

void tmMeasurement(char c){ //5TM soil moisture sensor

String command = "";

float Ea = 0.0;

float temp = 0.0;

float VWC = 0.0;

command += c;

command += "M!"; // SDI-12 measurement command format [address]['M'][!]

mySDI12.sendCommand(command);

delay(500); // wait a sec

mySDI12.flush();

command = "";

command += c;

command += "D0!"; // SDI-12 command to get data [address][D][dataOption][!]

mySDI12.sendCommand(command);

delay(500);

if(mySDI12.available() > 0){

int channel = mySDI12.parseInt();

Ea = mySDI12.parseFloat();

temp = mySDI12.parseFloat();

VWC = (4.3e-6*(Ea*Ea*Ea)) - (5.5e-4*(Ea*Ea)) + (2.92e-2 * Ea) - 5.3e-2 ; //the TOPP equation used to calculate VWC

Serial.print("Sensor:");

Serial.print(channel);

Serial.print(": Ea=");

Serial.print(Ea); //apparent dielectric permittivity

Serial.print(", VWC=");

Serial.print(VWC); //volumetric water content

Serial.print("%, Temp=");

Serial.print(temp); //Tempeerature

Serial.print("degC .... ");

}

mySDI12.flush();

}

Attachments:

results.png

2017-04-25 at 8:01 AM #2174
Shannon Hicks
Moderator
The graph looks more like a plot of temperature rather than VWC. Are you sure you’re plotting the right column of data? What are you using to actually record the data? Your sketch doesn’t output the data to a file or even print it in a easily-captured string out to the serial port, so I’m wondering how you collected multiple days of data. Plot your other variable and see what it looks like. The code also shows that you’re using 2 sensors. What does the data from the second sensor look like? The easiest way to see if a probe is working properly is to install 2 of them in the same location and in the same media and see if you get similar results for both of them.
2017-04-25 at 11:47 PM #2177
lilcano
Participant
Hello,

I just checked again and yes i am plotting the VWC. As for the collection of the data i am actually using an SD card shield on the arduino to store the data. As you can see from the image there are two curves each one for the different sensors placed at the same location. After getting this results i decided to take out the SD card shield and run the attach sketch with the arduino connected to my computer and unfortunately i obtain similar results on the arduino IDE serial monitor. please any ideas?
2017-04-26 at 8:53 AM #2178
Sara Damiano
Moderator
Please, like Shannon suggested, copy in your actual code using the “Add Code Snippet” button and actually attach your raw data, not a picture of it. Also, like Shannon said, please plot your EA and temperature to see how they look. And, again, like Shannon said, explain:

How were you testing the sensor? Was is installed outside or in a controlled environment? What kind of results were you expecting and what makes you think something is inconsistent?
2017-04-26 at 11:19 PM #2179
lilcano
Participant
Hello Sara,

Thanks for the reply, attached is a copy of the actual raw data and the sensor and arduino are actually places in a field(so not a controlled environment). I was expecting the VWC to reduce with time and not the sinusoidal behavior, Equally the Ea will give similar curve because its used to calculate the VWC using the Topps equation. Please can you take a look at the attached raw data and advice?
Attachments:
1. LOGGER11.csv

2017-04-27 at 12:08 PM #2181

Shannon Hicks

Moderator

I plotted the temperature and VWC on the same chart and you can see that they are very much linked together. Can you answer whether the sensor is completely buried in the soil, and if so how deep is it? If only the fiberglass tines are inserted into the soil but the rest of the sensor body is above ground and subjected to direct sunlight or drastic temperature swings, then I would assume that’s what causing the issue.

Can you also post the actual sketch you used on your Arduino board to capture your data and write it to the memory card. I can also show you how to record more significant digits for the VWC parameter so that you get finer resolution and a smoother curve. But I need you to post the actual sketch you used for the logger. And tell us exactly how the sensor was installed in the ground. Can you repeat this experiment indoors where the temperature is constant and in a pot of soil or somewhere where you can purposely vary the moisture content?

Attachments:

vwc-temp1.jpg

2017-04-30 at 5:09 PM #2191

lilcano

Participant

Hello Hicks,

Thanks for the reply, the sensors are buried completely in the soil as for the length i did not really measure that. Please see the attached file for the complete sketch running on the Arduino, and let me know what you think.

/*This is the first code for taking data from the 5TM sensor and showing it on the Arduino serial mornitor 
//The data is collected from the SDI12 sensor and timestamped then stored onto an SD card */
#include <SDI12.h>
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"


#define ECHO_TO_SERIAL   1 // echo data to serial port
#define WAIT_TO_START    0 // Wait for serial input in setup()

#define SYNC_INTERVAL 60000 // mills between calls to flush() - to write data to the card
uint32_t syncTime = 0; // time of last sync()

#define DATAPIN 5         // change to the proper pin for sdi-12 data pin, I prefer D7
SDI12 mySDI12(DATAPIN); 

//Define the number of sensors connected 

RTC_PCF8523 RTC; // define the Real Time Clock object

//the digitalpins that connect to the LEDS
#define redLEDpin 2
#define greenLEDpin 3
unsigned long previousMillis = 0;        
const long interval = 60000;        //set the interval (in milliseconds).  ex: 60000 = 60 seconds

// for the data logging shield, we use digital pin 10 for the SD cs line
const int chipSelect = 10;

// the logging file
File logfile;

//Function for handling errors that occur
void error(char *str)
{
  Serial.print("error: ");
  Serial.println(str);
  
  // red LED indicates error
  digitalWrite(redLEDpin, HIGH);

  while(1);
}

//Function for the working with the real time clock 
//and time stamping the data collected from the sensors
void timestamp(){
  
// fetch the time

  DateTime now = RTC.now();
  // log time
  //logfile.print(now.unixtime()); // seconds since 1/1/1970
  logfile.print(", ");
  logfile.print('"');
  logfile.print(now.year(), DEC);
  logfile.print("/");
  logfile.print(now.month(), DEC);
  logfile.print("/");
  logfile.print(now.day(), DEC);
  logfile.print(" ");
  logfile.print(now.hour(), DEC);
  logfile.print(":");
  logfile.print(now.minute(), DEC);
  logfile.print(":");
  logfile.print(now.second(), DEC);
  logfile.print('"');
#if ECHO_TO_SERIAL
  //Serial.print(now.unixtime()); // seconds since 1/1/1970
  Serial.print(", ");
  Serial.print('"');
  Serial.print(now.year(), DEC);
  Serial.print("/");
  Serial.print(now.month(), DEC);
  Serial.print("/");
  Serial.print(now.day(), DEC);
  Serial.print(" ");
  Serial.print(now.hour(), DEC);
  Serial.print(":");
  Serial.print(now.minute(), DEC);
  Serial.print(":");
  Serial.print(now.second(), DEC);
  Serial.print('"');
#endif //ECHO_TO_SERIAL
  
  }

 

//Function that runs at the start of the program once 
void setup () 
{
  //Debugging leds
     Serial.begin(57600);
     mySDI12.begin();
     pinMode(greenLEDpin, OUTPUT);
     pinMode(redLEDpin, OUTPUT);
     
     #if WAIT_TO_START
      Serial.println("Type any character to start");
      while (!Serial.available());
      #endif //WAIT_TO_START

          // initialize the SD card
      Serial.print("Initializing SD card...");
      // make sure that the default chip select pin is set to
      // output, even if you don't use it:
      pinMode(10, OUTPUT);
      
      // see if the card is present and can be initialized:
      if (!SD.begin(chipSelect)) {
        error("Card failed, or not present");
      }
      Serial.println("card initialized.");
      
      // create a new file
      char filename[] = "LOGGER00.CSV";
      for (uint8_t i = 0; i < 100; i++) {
        filename[6] = i/10 + '0';
        filename[7] = i%10 + '0';
        if (! SD.exists(filename)) {
          // only open a new file if it doesn't exist
          logfile = SD.open(filename, FILE_WRITE); 
          break;  // leave the loop!
        }
      }
      
      if (! logfile) {
        error("couldnt create file");
      }
      
      Serial.print("Logging to: ");
      Serial.println(filename);
    
      // connect to RTC
      Wire.begin();  
      if (!RTC.begin()) {
        logfile.println("RTC failed");
    #if ECHO_TO_SERIAL
        Serial.println("RTC failed");
    #endif  //ECHO_TO_SERIAL
      }

     digitalWrite(greenLEDpin, LOW);    //turn off the onboard LED to start with
     
      
     logfile.println("Sketch for sampling multiple SDI12 sensors");
     logfile.print(", ,");
     for(int i=0; i<=2; i++){
      logfile.print("      Sensor_Num, Ea, VWC(%), Temp(degC)       ");
      logfile.print(",");
      }
      logfile.println();
     #if ECHO_TO_SERIAL
     Serial.println("Sketch for sampling multiple SDI12 sensors");
    for(int i=0; i<=2; i++){
      Serial.print("      Sensor_Num, Ea, VWC(%), Temp(degC)       ");
      }
      #endif//ECHO_TO_SERIAL
      
     Serial.println();
     delay(1000); 
}

void loop () 
{ 
    //unsigned long currentMillis = millis(); 
    uint32_t currentMillis = millis();
    if(currentMillis - previousMillis >= interval || previousMillis == 0) {
   
       previousMillis = currentMillis;   
       digitalWrite(greenLEDpin, HIGH);     //turn on the onboard LED to show that samples are being taken
       Serial.print("Time: ");
       Serial.print(currentMillis/1000);  //print out the current time, in seconds
       logfile.print(currentMillis/1000);
       Serial.print("-----");
       timestamp();
       for (char j = '1'; j <= '3'; j++)  {        //go through channels 1 to 6 
         tmMeasurement(j);
         }
       logfile.println();
       Serial.println(); 
       digitalWrite(greenLEDpin, LOW);     //turn off the LED to show that samples are done
     
     // Now we write data to disk! Don't sync too often - requires 2048 bytes of I/O to SD card
    // which uses a bunch of power and takes time
  if ((millis() - syncTime) < SYNC_INTERVAL) return;
  syncTime = millis();
  
  // blink LED to show we are syncing data to the card & updating FAT!
  digitalWrite(redLEDpin, HIGH);
  logfile.flush();
  digitalWrite(redLEDpin, LOW);
     }
     
     delay(1000);
     
} 

void tmMeasurement(char c){        //5TM soil moisture sensor
  String command = ""; 
  float Ea = 0.0;
  float  temp = 0.0;
  float VWC = 0.0;
  command += c;
  command += "M!"; // SDI-12 measurement command format  [address]['M'][!]
  mySDI12.sendCommand(command); 
  delay(500); // wait a sec
  mySDI12.flush();

  command = "";
  command += c;
  command += "D0!"; // SDI-12 command to get data [address][D][dataOption][!]
  mySDI12.sendCommand(command);
  delay(500); 
  
    if(mySDI12.available() > 0){
        int channel = mySDI12.parseInt();
        Ea = mySDI12.parseFloat();
        temp = mySDI12.parseFloat();

      VWC = (4.3e-6*(Ea*Ea*Ea)) - (5.5e-4*(Ea*Ea)) + (2.92e-2 * Ea) - 5.3e-2 ;     //the TOPP equation used to calculate VWC


      //Serial.print("Sensor:");
      //logfile.print(",");
      logfile.print(",");
      logfile.print(channel);
      logfile.print(",");
      //Serial.print(": Ea=");
      logfile.print(Ea);             //apparent dielectric permittivity
      logfile.print(",");
      //Serial.print(", VWC=");
      logfile.print(VWC);            //volumetric water content 
      logfile.print(",");
      //Serial.print("%, Temp=");
      logfile.print(temp);           //Tempeerature 
      //logfile.print("degC  ....  ");
      
      #if ECHO_TO_SERIAL
      //Serial.print("Sensor:");
      Serial.print(",");
      Serial.print(channel);
      Serial.print(",");
      //Serial.print(": Ea=");
      Serial.print(Ea);             //apparent dielectric permittivity
      Serial.print(",");
      //Serial.print(", VWC=");
      Serial.print(VWC);            //volumetric water content 
      Serial.print(",");
      //Serial.print("%, Temp=");
      Serial.print(temp);           //Tempeerature 
      Serial.print("....  ");
      #endif
   } 
  mySDI12.flush(); 
}

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/*This is the first code for taking data from the 5TM sensor and showing it on the Arduino serial mornitor

//The data is collected from the SDI12 sensor and timestamped then stored onto an SD card */

#include <SDI12.h>

#include <SPI.h>

#include <SD.h>

#include <Wire.h>

#include "RTClib.h"

#define ECHO_TO_SERIAL 1 // echo data to serial port

#define WAIT_TO_START 0 // Wait for serial input in setup()

#define SYNC_INTERVAL 60000 // mills between calls to flush() - to write data to the card

uint32_t syncTime = 0; // time of last sync()

#define DATAPIN 5 // change to the proper pin for sdi-12 data pin, I prefer D7

SDI12 mySDI12(DATAPIN);

//Define the number of sensors connected

RTC_PCF8523 RTC; // define the Real Time Clock object

//the digitalpins that connect to the LEDS

#define redLEDpin 2

#define greenLEDpin 3

unsigned long previousMillis = 0;

const long interval = 60000; //set the interval (in milliseconds). ex: 60000 = 60 seconds

// for the data logging shield, we use digital pin 10 for the SD cs line

const int chipSelect = 10;

// the logging file

File logfile;

//Function for handling errors that occur

void error(char *str)

{

Serial.print("error: ");

Serial.println(str);

// red LED indicates error

digitalWrite(redLEDpin, HIGH);

while(1);

}

//Function for the working with the real time clock

//and time stamping the data collected from the sensors

void timestamp(){

// fetch the time

DateTime now = RTC.now();

// log time

//logfile.print(now.unixtime()); // seconds since 1/1/1970

logfile.print(", ");

logfile.print('"');

logfile.print(now.year(), DEC);

logfile.print("/");

logfile.print(now.month(), DEC);

logfile.print("/");

logfile.print(now.day(), DEC);

logfile.print(" ");

logfile.print(now.hour(), DEC);

logfile.print(":");

logfile.print(now.minute(), DEC);

logfile.print(":");

logfile.print(now.second(), DEC);

logfile.print('"');

#if ECHO_TO_SERIAL

//Serial.print(now.unixtime()); // seconds since 1/1/1970

Serial.print(", ");

Serial.print('"');

Serial.print(now.year(), DEC);

Serial.print("/");

Serial.print(now.month(), DEC);

Serial.print("/");

Serial.print(now.day(), DEC);

Serial.print(" ");

Serial.print(now.hour(), DEC);

Serial.print(":");

Serial.print(now.minute(), DEC);

Serial.print(":");

Serial.print(now.second(), DEC);

Serial.print('"');

#endif //ECHO_TO_SERIAL

}

//Function that runs at the start of the program once

void setup ()

{

//Debugging leds

Serial.begin(57600);

mySDI12.begin();

pinMode(greenLEDpin, OUTPUT);

pinMode(redLEDpin, OUTPUT);

#if WAIT_TO_START

Serial.println("Type any character to start");

while (!Serial.available());

#endif //WAIT_TO_START

// initialize the SD card

Serial.print("Initializing SD card...");

// make sure that the default chip select pin is set to

// output, even if you don't use it:

pinMode(10, OUTPUT);

// see if the card is present and can be initialized:

if (!SD.begin(chipSelect)) {

error("Card failed, or not present");

}

Serial.println("card initialized.");

// create a new file

char filename[] = "LOGGER00.CSV";

for (uint8_t i = 0; i < 100; i++) {

filename[6] = i/10 + '0';

filename[7] = i%10 + '0';

if (! SD.exists(filename)) {

// only open a new file if it doesn't exist

logfile = SD.open(filename, FILE_WRITE);

break; // leave the loop!

}

if (! logfile) {

error("couldnt create file");

}

Serial.print("Logging to: ");

Serial.println(filename);

// connect to RTC

Wire.begin();

if (!RTC.begin()) {

logfile.println("RTC failed");

#if ECHO_TO_SERIAL

Serial.println("RTC failed");

#endif //ECHO_TO_SERIAL

}

digitalWrite(greenLEDpin, LOW); //turn off the onboard LED to start with

logfile.println("Sketch for sampling multiple SDI12 sensors");

logfile.print(", ,");

for(int i=0; i<=2; i++){

logfile.print(" Sensor_Num, Ea, VWC(%), Temp(degC) ");

logfile.print(",");

}

logfile.println();

#if ECHO_TO_SERIAL

Serial.println("Sketch for sampling multiple SDI12 sensors");

for(int i=0; i<=2; i++){

Serial.print(" Sensor_Num, Ea, VWC(%), Temp(degC) ");

}

#endif//ECHO_TO_SERIAL

Serial.println();

delay(1000);

}

void loop ()

{

//unsigned long currentMillis = millis();

uint32_t currentMillis = millis();

if(currentMillis - previousMillis >= interval || previousMillis == 0) {

previousMillis = currentMillis;

digitalWrite(greenLEDpin, HIGH); //turn on the onboard LED to show that samples are being taken

Serial.print("Time: ");

Serial.print(currentMillis/1000); //print out the current time, in seconds

logfile.print(currentMillis/1000);

Serial.print("-----");

timestamp();

for (char j = '1'; j <= '3'; j++) { //go through channels 1 to 6

tmMeasurement(j);

}

logfile.println();

Serial.println();

digitalWrite(greenLEDpin, LOW); //turn off the LED to show that samples are done

// Now we write data to disk! Don't sync too often - requires 2048 bytes of I/O to SD card

// which uses a bunch of power and takes time

if ((millis() - syncTime) < SYNC_INTERVAL) return;

syncTime = millis();

// blink LED to show we are syncing data to the card & updating FAT!

digitalWrite(redLEDpin, HIGH);

logfile.flush();

digitalWrite(redLEDpin, LOW);

}

delay(1000);

}

void tmMeasurement(char c){ //5TM soil moisture sensor

String command = "";

float Ea = 0.0;

float temp = 0.0;

float VWC = 0.0;

command += c;

command += "M!"; // SDI-12 measurement command format [address]['M'][!]

mySDI12.sendCommand(command);

delay(500); // wait a sec

mySDI12.flush();

command = "";

command += c;

command += "D0!"; // SDI-12 command to get data [address][D][dataOption][!]

mySDI12.sendCommand(command);

delay(500);

if(mySDI12.available() > 0){

int channel = mySDI12.parseInt();

Ea = mySDI12.parseFloat();

temp = mySDI12.parseFloat();

VWC = (4.3e-6*(Ea*Ea*Ea)) - (5.5e-4*(Ea*Ea)) + (2.92e-2 * Ea) - 5.3e-2 ; //the TOPP equation used to calculate VWC