pH/ORP stamp using UART port

The device communicates via the serial port.

Serial.println("led(on)"); // turn the LED on

Serial.println("read(22.0)"); // Read the pH level assuming temp is 22.0 degrees

Once you've told the sensor to do something, you need to read it's reply.

char inData[24];
byte index = 0;
while(Serial.available() > 0 && index < 24)
{
   inData[index] = Serial.read();
   index++;
   inData[index] = '\0';
}

Then, do whatever you need to with inData.