Negative power displayed on a Clamp-on Power Logger

QI measured the power trend using a Clamp-on Power Logger, but the power value is negative. Why does this happen?

A

Unless the load is generating power, the value shall be positive (consumption).  Please check to see  if the clamp-on sensor is positioned in the reverse direction, by verifying that the arrow marking on the sensor head is pointing in the direction from source to load.