Technical Characteristics and Control Intelligence
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Dual Channel Flexibility: The FMU90 can process signals from two independent sensors. This allows for the calculation of average levels in large silos, the sum of two tanks, or the difference in level across a mechanical rake or screen to trigger cleaning cycles.
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Integrated Flow Curves: For water and wastewater applications, the FMU90 comes pre-programmed with flow curves for the most common flumes and weirs. This enables “plug-and-play” flow measurement without the need for manual 32-point linearization.
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Advanced Pump and Rake Control: Beyond simple measurement, the FMU90 features up to 6 relays. These can be configured for complex pump alternating logic, rake control, tendency alarms (rising/falling levels), or as pulse outputs for external flow totalizers.
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Diagnostic Visualization: The 6-line plain text display provides on-site envelope curve diagnostics. This is essential for distinguishing between the true material surface and interference echoes caused by foaming, turbulence, or tank internal structures.
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Intelligent Time-of-Flight Correction: To maintain accuracy over long distances (up to 45 m), the device utilizes temperature data from the FDU sensors or an external sensor to adjust the speed of sound calculations in real-time.
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Seamless Sensor Detection: The FMU90 automatically identifies any connected FDU9x series sensor, simplifying the commissioning process and reducing the risk of configuration errors.
Technical Specification Matrix
| Feature | Technical Details |
| Measuring Principle | Ultrasonic (Time-of-Flight) |
| Sensor Inputs | 1 or 2 channels (FDU9x series) |
| Max. Range | Up to 45 m (148 ft) (Sensor dependent) |
| Mounting Options | Field housing (IP66) or Top-hat rail (IP20) |
| Relays | Up to 6 (for alarms, pump control, pulse output) |
| Totalizers | 3 totalizers and 3 counters |
| Accuracy | +/- 2 mm + 0.17% of measured distance |
Primary Applications
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Storm Water Overflow Basins: Simultaneously measuring the water level and the discharge flow during overflow events with a single system.
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Rake and Screen Control: Measuring the level difference between the upstream and downstream sides of a screen to automate debris removal.
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Pump Stations: Comprehensive control of multiple pumps including alternating start/stop cycles to ensure even wear and prevent dry-running.
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Open Channel Flow: High-precision flow monitoring in municipal wastewater treatment plants using standardized flumes (Parshall, Venturi, etc.).
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Backwater Detection: Monitoring flow in channels and detecting if downstream blockages (backwater) or sludge buildup are affecting the measurement accuracy.
