/* Water Level Meter
https://www.instructables.com/Measuring-water-level-with-ultrasonic-sensor/
Measuring water level with ultrasonic sensor HR S04.
Arduino IDE 1.5.8
*/




int trig = 12;

int echo = 11;



void setup()
{
  
Serial.begin(9600);
  
pinMode(trig, OUTPUT);
  
pinMode(echo, INPUT); 
}



void loop()

{
  
long t = 0, h = 0, hp = 0;
  
  
// Transmitting pulse
  
digitalWrite(trig, LOW);
  
delayMicroseconds(2);
  
digitalWrite(trig, HIGH);
  
delayMicroseconds(10);
  
digitalWrite(trig, LOW);
  
  
// Waiting for pulse
  
t = pulseIn(echo, HIGH);

// Calculating distance 
  
h = t / 58;

h = h - 6;  // offset correction
  
h = 50 - h;  // water height, 0 - 50 cm

hp = 2 * h;  // distance in %, 0-100 %

// Sending to computer
  
Serial.print(hp);
  
// Serial.print(" cm\n");
  
Serial.print("\n");
  
  
delay(1000);
}