Potential HR-380 P
The HR-380 P Potential probe measures specific resistance of surrounding rocks which, after the data evaluation, helps to determine the lithological boundary of permeable layers in a borehole or to follow structures of coal seams.
The Potential probe has the distance between unpaired electrodes smaller than the distance from the paired electrodes M - A0, A1.
Difference between the potential and gradient resistivity measurements are in shapes of resulting curves. The curve measured by a potential probe is symmetric in the point of maximal anomaly.
If the thickness of a layer is smaller than the length of the probe, the resulting curve shows minimal value.
Depth of investigation is given by the length of the probe: L = A to M.
A gradient probe (HR-380 Glu) is better at detecting of underlying or overlying boundaries of rocks. The shape of its resulting curve is non symmetrical. Length of the probe L = A to 0 gives N the depth of investigation.
The measured values of Rap and Rag are affected by the borehole diameter and by the specific resistivity of the mud cake.

Probe Parameters
Available in diameters | 38 mm and 45 mm |
Length | 2000 mm |
Weight | 5,0 kg |
Max. Working Pressure / Temperature | 10 MPa / 75 °C |
Power Supply | 45 Vdc @ 120 mA |
Excitation frequency is 8 Hz; Operated on one conductor cable.
Output pulses of amplitudes/widths 8V / 6 µs (values are adjustable).
Measurement
The shorter channel (0,10 m) is active during winching the probe down. After reversing the direction of movement the other electrode (0,4 m channel) is activated.