Solinst Model 102M Coaxial Cable Mini Water Level Meter With P4 Probe. The Solinst Model 102M P4 Probe Mini Water Level Meter is designed to measure groundwater levels in small diameter tubes and piezometers. A choice of two small diameter probe designs are attached to a narrow coaxial cable. The cable has a heavy-duty polyethylene jacket and stainless steel coaxial conductors for durability and strength. Permanent markings are precisely laser etched on the cable every 1/100 ft. or each millimeter. A standard 9 volt battery, housed in an easy-access battery drawer, powers the Water Level Meter. When the probe enters water, a light and clearly audible buzzer are activated. The water level is then determined by taking a reading directly from the cable at the top of the well casing or borehole. A sensitivity control allows the buzzer to be turned off while in cascading water and ensures a clear signal in both high and low conductivity conditions.