void setup()
{
Serial.begin(9600);
}
void loop()
{
int sensorValue;
sensorValue = random(0,1024); // analogRead(A0); // 0...1023
Serial.print( "Bad value: ");
auto n = Serial.print( sensorValue * 5000 / 1023.0); // <-- Bad
Serial.print( " mV.");
for( int i=n; i<8; i++)
Serial.print( " ");
Serial.print( "Good value: ");
float voltage = float( sensorValue) * 5.0 / 1024.0; // <-- Good
Serial.print( voltage);
Serial.println( " V.");
delay(1000);
}