Estimated reading time: 3 minutes
Moisture sensors for concrete plants have their similarities and differences. Since you will have variations, even in the same bin, the stream discharging into your scale will have variations from one side to the other. Find the best moisture sensor for your application.
Moisture sensor types
- Microwave sensors (probes) are much better than the older resistive or capacitive types because they are unaffected by minerals or salts in the sand or aggregate. AquaSense (at right), manufactured at our Montreal plant, is a good example. You can position it to measure the center of the flowing material, giving a good average. And it has the lowest cost, plus a 10 year guarantee!
- Others, such as Hydronix and Command Alkon, although using a different measurement technique, are equal if you apply them correctly. They are all sensitive to variation in density and require equally compacted material to give consistent results. They all measure total moisture but they can read surface moisture by subtracting the assumed internal moisture during the calibration process. All are limited by the aggregate size, giving poor accuracy on aggregate sizes over 3/8″.
- Polarmoist, by Polarmatic, measures surface moisture only. It uses a near-infra-red light beam to measure reflected light from the moist particles as they fall, or on a conveyor belt. Because it measures the surface of the stream, it cannot measure deep into the flow. This is its worst drawback. You can use it with aggregates over 1/2″ (12 mm) although the manufacturer does not specify its accuracy in this case. Scale-Tron is a Polarmoist dealer.
- Sono-Vario by Imko (at right). It uses a different technique which is less sensitive to density. Its measurement volume is much bigger than the others above. As a result, it gives you superior accuracy in most applications. It measures total moisture but can read surface moisture by subtracting the assumed internal moisture during the calibration process. It can measure up to 1.25″ (32 mm) aggregates within 0.2% accuracy; a big plus. Scale-Tron is a Sono-Vario dealer.
For more information on Scale-Tron’s range of moisture sensors or probes, and to find the best moisture sensor for your application, visit the Moisture Measurement page.