Add emon lib for a later non invasive current sensor.

libraries/EmonLib/examples/current_only/current_only.ino

@@ -0,0 +1,20 @@
+// EmonLibrary examples openenergymonitor.org, Licence GNU GPL V3
+
+#include "EmonLib.h"                   // Include Emon Library
+EnergyMonitor emon1;                   // Create an instance
+
+void setup()
+{  
+  Serial.begin(9600);
+  
+  emon1.current(1, 111.1);             // Current: input pin, calibration.
+}
+
+void loop()
+{
+  double Irms = emon1.calcIrms(1480);  // Calculate Irms only
+  
+  Serial.print(Irms*230.0);	       // Apparent power
+  Serial.print(" ");
+  Serial.println(Irms);		       // Irms
+}