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Topic: pH Meter problem (Read 2730 times)previous topic - next topic

Wecuyx

Jun 08, 2017, 10:03 am
I have a temperature and pH sensor connected to my Arduino Uno Wifi with a Base Shield 2.0. On the Base Shield, there is a switch for 3.3v and 5v. If the switch is towards 3.3v, i will have a normal pH value(Water: about 7.0) but my temperature value will be low as 17Degrees(Suppose to be around 32).
If i switch to 5V on my Base Shield, My pH value will increase up to around 9-10 pH value while my Temperature will be correct. How can i adjust so that i will have both value correct?

Wecuyx

#1
Jun 08, 2017, 10:10 am
This is my Sketch for pH and Temperature:
/*
# This sample code is used to test the pH meter V1.0.
# Editor : YouYou
# Ver    : 1.0
# Product: analog pH meter
# SKU    : SEN0161
*/
#define SensorPin A0            //pH meter Analog output to Arduino Analog Input 0
#define Offset 0.00            //deviation compensate
#define LED 13
#define samplingInterval 20
#define printInterval 800
#define ArrayLenth  40    //times of collection
int pHArray[ArrayLenth];   //Store the average value of the sensor feedback
int pHArrayIndex=0;

//Temperature
int a;
float temperature;
int B=3975;                  // B value of the thermistor
float resistance;

void setup(void)
{
pinMode(LED,OUTPUT);
Serial.begin(9600);
Serial.println("pH meter experiment!");    //Test the serial monitor
}
void loop(void)
{
static unsigned long samplingTime = millis();
static unsigned long printTime = millis();
static float pHValue,voltage;
if(millis()-samplingTime > samplingInterval)
{
if(pHArrayIndex==ArrayLenth)pHArrayIndex=0;
voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;
pHValue = 3.5*voltage+Offset;
samplingTime=millis();
}
if(millis() - printTime > printInterval)   //Every 800 milliseconds, print a numerical, convert the state of the LED indicator
{
Serial.print("Voltage:");
Serial.print(voltage,2);
Serial.print("    pH value: ");
Serial.println(pHValue,2);
printTime=millis();
}
//Temperature
resistance=(float)(1023-a)*10000/a;                      // get resistance
temperature=1/(log(resistance/10000)/B+1/298.15)-273.15;     // calc temperature
delay(1000);                                                 // delay 1s
Serial.print("Current Temperature is ");
Serial.println(temperature);
}
double avergearray(int* arr, int number){
int i;
int max,min;
double avg;
long amount=0;
if(number<=0){
Serial.println("Error number for the array to avraging!/n");
return 0;
}
if(number<5){   //less than 5, calculated directly statistics
for(i=0;i<number;i++){
amount+=arr;
}
avg = amount/number;
return avg;
}else{
if(arr[0]<arr[1]){
min = arr[0];max=arr[1];
}
else{
min=arr[1];max=arr[0];
}
for(i=2;i<number;i++){
if(arr<min){
amount+=min;        //arr<min
min=arr;
}else {
if(arr>max){
amount+=max;    //arr>max
max=arr;
}else{
amount+=arr; //min<=arr<=max
}
}//if
}//for
avg = (double)amount/(number-2);
}//if
return avg;
}

jremington

#2
Jun 08, 2017, 04:59 pm

This line assumes that the voltage reference value is 5V. Is it at all times?

Code: [Select]
`voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;`

allanhurst

#3
Jun 12, 2017, 11:21 pm
What is a 'base shield'? what are it's specifications?

without this we can't help.

Allan

#4
Aug 30, 2018, 06:09 am
/*
# This sample code is used to test the pH meter V1.0.
# Editor : YouYou
# Ver    : 1.0
# Product: analog pH meter
# SKU    : SEN0161
*/
#define SensorPin A0            //pH meter Analog output to Arduino Analog Input 0
#define Offset 0.00            //deviation co*******2mpensate
#define LED 13
#define samplingInterval 20
#define printInterval 800
#define ArrayLenth  40    //times of collection
int pHArray[ArrayLenth];   //Store the average value of the sensor feedback
int pHArrayIndex=0;
const int buzzer = 9;
void setup(void)
{
pinMode(LED,OUTPUT);
pinMode(buzzer, OUTPUT);
Serial.begin(9600);
Serial.println("pH meter experiment!");    //Test the serial monitor
}
void loop(void)
{
static unsigned long samplingTime = millis();
static unsigned long printTime = millis();
static float pHValue,voltage;
if(millis()-samplingTime > samplingInterval)
{
if(pHArrayIndex==ArrayLenth)pHArrayIndex=0;
voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;
pHValue = 3.5*voltage+Offset;
samplingTime=millis();
}
if(millis() - printTime > printInterval)   //Every 800 milliseconds, print a numerical, convert the state of the LED indicator
{
Serial.print("Voltage:");
Serial.print(voltage,2);
Serial.print("    pH value: ");
Serial.println(pHValue,2);
if(pHValue <=4.0){
digitalWrite(buzzer,HIGH);
delay(1000);
}
if(pHValue >4.0){
digitalWrite(buzzer,LOW);
}
printTime=millis();
}
}
double avergearray(int* arr, int number){
int i;
int max,min;
double avg;
long amount=0;
if(number<=0){
Serial.println ("Error number for the array to avraging!/n");
return 0;
}
if(number<5){   //less than 5, calculated directly statistics
for(i=0;i<number;i++){
amount+=arr;
}
avg = amount/number;
return avg;
}else{
if(arr[0]<arr[1]){
min = arr[0];max=arr[1];
}
else{
min=arr[1];max=arr[0];
}
for(i=2;i<number;i++){
if(arr<min){
amount+=min;        //arr<min
min=arr;
}else {
if(arr>max){
amount+=max;    //arr>max
max=arr;

}else{
amount+=arr; //min<=arr<=max
}
}//if
}//for
avg = (double)amount/(number-2);
}//if
return avg;
}

Delta_G

#5
Aug 30, 2018, 06:51 pm
I have a temperature and pH sensor connected to my Arduino Uno Wifi with a Base Shield 2.0. On the Base Shield, there is a switch for 3.3v and 5v. If the switch is towards 3.3v, i will have a normal pH value(Water: about 7.0) but my temperature value will be low as 17Degrees(Suppose to be around 32).
If i switch to 5V on my Base Shield, My pH value will increase up to around 9-10 pH value while my Temperature will be correct. How can i adjust so that i will have both value correct?
Are you sure your water should read at 7?  While that is theoretical neutral water, it would be quite unusual to measure that value without buffering the water to maintain it.  Normally water out of the tap is around the high 8's or even low 9's depending on corrosion control measures.

Get a known pH standard to check against.  You can't use water.
|| | ||| | || | ||  ~Woodstock

Please do not PM with technical questions or comments.  Keep Arduino stuff out on the boards where it belongs.

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