Radar Moisture Meters SONO-SILO

The SONO-SILO is a robust, inline TDR radar moisture sensor specifically designed for continuous, real-time measurement of moisture, electrical conductivity (mineral/cement content indicator) and temperature in bulk materials such as sand, gravel, crushed stone and other aggregates. Manufactured from stainless steel (V2A 1.4301) with a highly wear-resistant rectangular aluminium-oxide ceramic window, it is installed in silos, bins, hoppers, fluidized-bed dryers, under silo discharge valves or directly in mixers via welded flanges. The probe (Ø 55 mm × 350 mm) can be extended with pipes. A military-grade MIL connector ensures reliable connection even in abrasive, dusty and high-pressure environments.

Principle of Operation

SONO-SILO uses patented TRIME®-TDR technology at 1 GHz radar frequency. A high-frequency electromagnetic pulse (600 MHz – 1.2 GHz) is transmitted along the waveguides, creating an electromagnetic field that penetrates the surrounding bulk material. Propagation time (1-picosecond resolution) determines the dielectric constant and thus moisture content (%). Conductivity (EC-TRIME / RbC, 0–12 dS/m) is measured simultaneously to indicate mineral concentration. The internal processor performs up to 10,000 measurements per second, validates, filters and averages them (~280 ms cycle). Six operating modes are available: CA (cyclic averaging), CF (floating averaging for inhomogeneous flows), CH (hold), CC (cumulative for batch processes), CS (sequential), CK (Kalman filter). Automatic air/water calibration, temperature compensation and gap filtering ensure stable, accurate readings even when material flow is intermittent.

Specifications

• Moisture range: 0 % to saturation (up to 90 % with special calibration); typical 0–20 %

• Accuracy: ±0.1 %

• Conductivity (EC-TRIME/RbC): 0–12 dS/m

• Temperature range: 0 … +70 °C (material); self-heating compensation

• Power supply: +12 … +24 V DC stabilised, 3 W total

• Analogue outputs: 2 × 0/4–20 mA (Output 1: moisture, adjustable range; Output 2: conductivity or temperature); optional 0–10 V via 500 Ω resistor; max. load 500 Ω

• Digital interfaces: RS485 + IMP-Bus (galvanically isolated current loop – no shielding or termination required)

• Dimensions: Ø 55 mm × 350 mm (extendable with pipes)

• Protection: Gas- and water-tight flange mounting; MIL connector

• Special features: Automatic air/water calibration; up to 15 calibration curves (linear/non-linear up to 5th order); universal Cal9 curve for sand/gravel/crushed stone (1.5–1.9 t/m³); gap & intermittent-flow filtering; cumulative batch mode (CC/CH) without external triggers

Main Application Areas

• Continuous moisture & mineral content monitoring in concrete aggregate silos and bins

• Under silo discharge valves for short-cycle, high-accuracy measurement

• Fluidized-bed dryers, conveyor belts and screw conveyors

• Sand & gravel classification (0–32 mm) and crushed stone (0–8 mm)

• Automated quality control in ready-mix and precast concrete plants

• Integration into PLC systems for water dosing and recipe optimisation

Advantages of SONO SILO Radar Moisture Meters

• Extremely high accuracy (±0.1 %) and repeatability in abrasive, dusty and intermittent flows

• Superior to capacitive (5–40 MHz) and microwave (>2 GHz) sensors – virtually unaffected by temperature, salinity, dust or material density

• Automatic air/water calibration and long-term stability without re-calibration

• Highly wear-resistant ceramic window and stainless-steel construction

• Intelligent gap filtering and six averaging modes for stable readings even when silo is emptying

• Simultaneous moisture + conductivity measurement → reliable mineral content control

• IMP-Bus enables interference-free networking over long distances without shielding

• Easy flange mounting and pipe extension for virtually any silo geometry

• Significant reduction of water/cement errors → consistently high concrete quality and lower production costs