A small sensor in a production logging tool that distinguishes between hydrocarbon and water in its vicinity as it is moved up and down a production well. The electric probe was the first type of local probe to be introduced, appearing initially in the early 1990s. Electric probes measure the local and average holdup of water and give an image of the flow structure across the well.

Most electric probes emit a high-frequency current and measure the amplitude of the signal, and hence the impedance, of the fluid in a small sphere near the probe. The output is designed to be digital, indicating conductance when the probe is in front of water, and no conductance when it is in front of hydrocarbon. The water must have a certain minimum salinity, below which the device will not work.