Static water level ruler, especially suitable for use in narrow pipes.With 9 V battery, smaller diameter sensor connection works on coaxial cable.The coaxial cable is marked with a scale.When the sensor touches the water surface, there will be a sound prompt and indicator light on the winch. Just record the ruler to read it.Its sensor diameter is only 6 mm (another 10 mm is optional), and the front end of the sensor adopts a joint-shaped counterweight structure, making the probe more flexible and move freely in the narrow monitoring pipeline.There are two sensors to choose from.