Blumat Digital Moisture Meter
The ceramic extension is soaked in and filled with water, just like a Blumat sensor. When this is inserted into the growing medium, the medium exerts a pressure on the water inside the cone. When the medium is more dry, it pulls harder on the water inside the cone. When the medium is more moist, the force pulling inside the cone is less. These forces of pressure correlate to different readings on the meter. A reading of 0 indicates standard water, while a high reading of 750 or so indicates sawdust completely void of moisture. The digital moisture meter is a tensiometer, but indicates moisture levels using pressure as a correlative.