Solinst Model 102M [114909] Coaxial Cable Water Level Meter With P4 Probe & Metric Increments, 30m. 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.