Polarmoist, an alternative way to measure surface moisture
Because it uses uses near-infrared (IR) light, Polarmoist can measure the surface moisture of sand, aggregates and other granular materials. It is placed to view the materials as they pass by on a belt or flow out of a hopper, without making contact. In comparison, AquaSense and AquaMix must be in contact with the material and they measure bulk moisture (but can be calibrated to read surface moisture percentage).
Polarmoist is the only system that can measure the surface moisture content of large aggregates (greater than 3/8″ or 10 mm). Capacitance and microwave methods show too much variation. The sensor uses an LED light source and solid-state detection. It has a narrow-beam lens to focus on the stream of material. A low volume air supply keeps the lens clear of dust. This is necessary in most applications such as sand, because a lot of dust is raised as it is handled. Download Polarmoist brochure
Conveyor belt: You should position the IR moisture level sensor so that its field of view includes the sand on the belt. Do not include any part of the belt itself in the sensor’s field of view. The sensor averages the signal as the material travels past the viewing zone.
Clam gate: You should position the IR moisture level sensor to view the falling material between the gate and the hopper or belt. The averaging starts when the gate opens and continues while the material is falling.
Mixer: You should position the IR sensor to view the surface of the mixing material. If water is added, time must be allowed for the water to be thoroughly mixed into the material. This minimizes the error in the surface moisture measurement.