I just checked again and yes i am plotting the VWC. As for the collection of the data i am actually using an SD card shield on the arduino to store the data. As you can see from the image there are two curves each one for the different sensors placed at the same location. After getting this results i decided to take out the SD card shield and run the attach sketch with the arduino connected to my computer and unfortunately i obtain similar results on the arduino IDE serial monitor. please any ideas?