DFRobot Gravity TDS Sensor not working

Using Arduino Sensors
1

Hello,
I have a brand new TDS sensor from DFRobot, and I plugged it into my Arduino Mega as follows:
TDS - to GND
TDS + to 3V3
TDS A to A1
The DFRobot board lights up and the probe is attached properly. When I run the following code straight from DFRobot examples, I get a constant reading of 619ppm no matter what (probe in open air, tap water, and salt water).

#include "GravityTDS.h"

#include <EEPROM.h>
 
#define TdsSensorPin A1
GravityTDS gravityTds;
 
float temperature = 25,tdsValue = 0;
 
void setup()
{
    Serial.begin(115200);
    gravityTds.setPin(TdsSensorPin);
    gravityTds.setAref(3.3);  //reference voltage on ADC, default 5.0V on Arduino UNO
    gravityTds.setAdcRange(1024);  //1024 for 10bit ADC;4096 for 12bit ADC
    gravityTds.begin();  //initialization
}
 
void loop()
{
    //temperature = readTemperature();  //add your temperature sensor and read it
    gravityTds.setTemperature(temperature);  // set the temperature and execute temperature compensation
    gravityTds.update();  //sample and calculate
    tdsValue = gravityTds.getTdsValue();  // then get the value
    Serial.print(tdsValue,0);
    Serial.println("ppm");
    delay(1000);
}

I also ran this code and verified that a simple analog read isn't changing either. When I run this, I get a constant analog read of 489 no matter what.

#define TdsSensorPin A1

void setup() {
  Serial.begin(115200);
  pinMode(TdsSensorPin, INPUT);
}

void loop() {
  int sensorValue = analogRead(TdsSensorPin);
  Serial.println(sensorValue);
  delay(1000);
}

Does anyone know what the issue might be? I'm tempted to say I received a faulty sensor!

2

I am too. I have one of those and it works as expected, so ask for a refund or replacement.

However, double check that the ADC input actually works, and that the wiring is good. A DMM is useful to check lead and pin connectivity.