pH sensor problems

Hi,

I have a nodemcu 1.0 which I want to connect to a ph sensor from aliexpress (https://www.aliexpress.com/item/PH-sensor-Module-1pc-PH-Sensor-Module-V1-1-1pc-PH-Probe-for-AVR-51-PH/32683361619.html)

When I connect the probe on A0 the interface board gives me some values (with a simple code from reading analog values) but the probe does not seem to provide any variety in voltage to indicate changes in pH. Even if I disconnect the probe I still get the same values.. It gives me a voltage of approx 2.5. Has anyone come across a similar problem with these type of sensors?

I feel like there might be just a stupid reason for this not to be working.. so maybe someone who have used similar sensors have an idea of what I am doing wrong..

the code:

#define SensorPin 0            //pH meter Analog output to Arduino1 Analog Input 0
#define Offset 0.00            //deviation compensate
unsigned long int avgValue;     //Store the average value of the sensor feedback
void setup()
{
  Serial.begin(9600);  
  Serial.println("Ready");    //Test the serial monitor
}
void loop()
{
  

  Serial.print("Raw analog:");
  Serial.print(analogRead(SensorPin));
  Serial.println(" ");
  float phValue=(float)analogRead(SensorPin)*5.0/1024; //convert the analog into millivolt
  Serial.print("Volt:");
  Serial.print(phValue);
  Serial.println(" ");
  phValue=3.5*phValue+Offset;                      //convert the millivolt into pH value
  Serial.print("    pH:");  
  Serial.print(phValue,2);
  Serial.println(" ");
  delay(1000);
}

not looked the code, but have you connected the 0v lines together?

Perhaps some answers in this thread
https://forum.arduino.cc/index.php?topic=336012.0
and in this link : https://scidle.com/how-to-use-a-ph-sensor-with-arduino/
++
C

crustyourmind:
Perhaps some answers in this thread
Help with Ph sensor pin abbreviations - Sensors - Arduino Forum
and in this link : https://scidle.com/how-to-use-a-ph-sensor-with-arduino/
++
C

crustyourmind: Yes, I had a look in that thread. Didn't give any solutions.. Tried varies codes from the thread even though the problem is really getting the interface (sen0161) to pick up voltage from the probe. So as long as i read the input on A0 correctly (as I believe I do) the sen0161 board should do the rest, no?

hammy:
not looked the code, but have you connected the 0v lines together?

Hammy: I connected the three wires on the interface board (sen0161) to 5V output pin, ground and Analog0 on my nodemcu. The probe is connected to the sen0161 with a bnc connection. What do you mean Gnd lines toghether?

This pH board should not be much more than an amplifier, the output being the voltage of the pH probe plus an offset (probably 2.5V)

With no probe connected the input should be floating, and go anywhere.

The NodeMCU has no 5V output pin. It does have a VU pin which is the USB voltage, which only supplies power when connected to the USB. The device itself operates at 3.3V.

Did you find any solutions to this? , because I am facing the same problem also I am a beginner . At module calibration when short circuit the inner and the outer pin at bnc connector I get 2.5volt so I suppose that the module works fine?

thanks a lot

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