Direct Assessment & Guided Wave Testing

Voltage Gradients and Earth Current Vectors
• By collecting three half cell readings simultaneously in a grid
pattern, voltage gradients can be measured between the half cell
• These voltage gradients can then be converted into earth current
vectors in a polar coordinate system, allowing for easier data
interpretation in a real world environment
• In the example on the right,
the area potentials
measured result in 100 mV
gradients in the x and y
coordinate directions,
resulting in a 45 degree
earth current gradient
-400 mV
-500 mV
-400 mV
SLIDE 18