E+H FMU90-R11CA131AA1A Ultrasonic Level Transmitter

The FMU90 is a remote ultrasonic level transmitter unità principale. It requires an external FDU series ultrasonic sensore (FDU90/91/92/93/95, ecc.). It is suitable for liquid, sludge and solid level measurement, as well as open channel flow measurement and pump alternation control.

✅ Model Decoding FMU90-R11CA131AA1A

FMU90-R11CA131AA1A

1. R: Level measurement + pump alternation control function
2. 1: Field housing, PC polycarbonate, IP66 / NEMA4X
3. 1: Backlit display with keypad operation
4. C: 90~253V AC power supply
5. UN: 1 sensor input (for FDU sensor connection)
6. 3: 3-channel SPDT passive relay outputs
7. 1: 1-channel 4~20mA HART analog output
8. UN: No additional auxiliary input
9. UN: Basic data logging version
10. 1: Multilingual support (German/English/French/Spanish/Italian/Portuguese/Dutch)
11. UN: No extra options

📌 Core Technical Specifications

Principio di misurazione: Ultrasonic time-of-flight method with built-in sound velocity temperature compensation

Ingresso: 1 canale, compatible with FDU8x / FDU9x series ultrasonic sensors

Uscita analogica: 4~20mA HART

Uscita commutata: 3 SPDT relays for high/low level alarm and pump alternation control

Alimentazione elettrica: 90–253 VAC

Alloggiamento: Policarbonato, IP66, wall-mounted for field installation

Precisione: ±2 mm + 0.17% of measuring distance

Diagnostica: Echo envelope curve display, compatible with FieldCare configuration software

Linearization: Up to 32-point free linearization; built-in flume profiles for open channel flow

Funzioni: Continuous level measurement, volume calculation, pump alternation control, rake control, flow totalization, level alarm

🧰 Typical Matching Sensor Selection Reference

📋 Applicable Industries

Municipal wastewater plants, acquedotto, serbatoi di stoccaggio chimico, mining silos, open channels, rainwater tanks. Non-contact measurement, suitable for viscous sewage containing air bubbles.

⚠️ Common Fault Points

1. Blanking Distance: A dead zone directly below the sensor where measurement is impossible. Must be avoided during selection and installation.
2. Foam, heavy dust and dense steam attenuate ultrasonic waves and cause echo loss.
3. Brackets and pipes inside tanks generate false echoes; false echo suppression via software is required.
4. Remote design. Special coaxial cable connects main unit and sensor, with a maximum allowable cable length.

🔁 Alternative Solutions

1. E+H same series: FMU90-R11CA231AA1A (dual sensor input)
2. Alternativa domestica: Remote ultrasonic level host supporting 4-20mA + relè; sensor interface protocol must be verified.
3. Radar alternative: Radar FMR series is preferred for working conditions with heavy foam or steam.

📎 Documentation & Comunicazione

Software di configurazione: FieldCare, HART DTM

Manual codes: TI00397FZH, BA00293FZH

Codice SA: 90261000 (liquid level measuring instruments)

E+H FMU90-R11CA131AA1A (Prosonic S) Field Application Cases

Not Pepperl+Fuchs, but Endress+Hauser. FMU90-R11CA131AA1A features single sensor input, 3 SPDT relays, 4~20mA HART output and native pump alternation function. All cases below match this model’s hardware capability.

Caso 1: Municipal Wastewater Plant – Sump Level Measurement + Duty/Standby Pump Alternation (Most Typical)

Configurazione: FMU90-R11CA131AA1A + FDU91 (10m ultrasonic sensor)

Condizioni di lavoro: Wastewater lift pump sump with suspended solids and minor foam. Two submersible sewage pumps. Requisiti: automatic alternation, high/low level alarm, high-high level interlock.

Implementation Logic

1. FMU90 continuously acquires liquid level; 4~20mA HART signal transmits data to PLC / host system.
2. Relay allocation:

Relè 1: High level to start Pump A

Relè 2: High-high level alarm + standby Pump B startup. Automatic alternation: Pump B will start first next cycle (native pump alternation function of transmitter).

Relè 3: Low level to stop pumps

3. Built-in echo suppression filters false echoes from well brackets and pipes. Echo envelope curve can be viewed locally on the main unit.

Vantaggi: No separate pump controller required. One unit integrates level acquisition, pump logic and alarm. Non-contact sensor prevents corrosion by sewage and sludge.

Limitazione: Thick foam attenuates ultrasonic waves. Radar transmitter is recommended for heavy foam applications.

Caso 2: Waterworks Sedimentation Tank – Open Channel Parshall Flume Flow Metering

Configurazione: FMU90-R11CA131AA1A + FDU91

Condizioni di lavoro: Parshall flume at water plant outlet. Continuous open channel flow measurement and total volume accumulation, flow over-limit alarm.

Implementation Logic

1. Transmitter stores standard Parshall flume profile. Instantaneous flow and total volume are calculated from liquid level.
2. 4~20mA outputs instantaneous flow; relay triggers flow over-limit alarm.
3. One sensor measures level and flow simultaneously. Built-in flow totalizer supports 3 independent counters.

Applicazione: Water intake / drainage flow monitoring for environmental protection, compatible with environmental data acquisition terminal.

Caso 3: Rainwater Detention Tank – Overflow Tank Level & Overflow Flow Monitoring

Configurazione: FMU90-R11CA131AA1A + FDU92 (20portata m)

Condizioni di lavoro: Urban rainwater overflow tank with sharp level fluctuation in rainy season. Monitor tank level and weir overflow flow, record rainwater overflow volume.

Implementation Logic: Single ultrasonic sensor measures liquid level. Overflow flow is calculated automatically via weir model. Relay activates alarm during overflow. Low-power monitoring in dry season.

Official E+H typical application: Integrated level & overflow flow measurement for rainwater overflow tanks, natively supported by FMU90.

Caso 4: Chemical Park Wastewater Equalization Tank – Sludge Level Monitoring

Configurazione: FMU90-R11CA131AA1A + FDU91F corrosion-resistant sensor

Condizioni di lavoro: Chemical wastewater equalization tank with corrosive wastewater and settled sludge. Monitor sludge interface / tank liquid level and interlock with sludge scraper.

Implementation Logic: Continuous level measurement. Relay triggers high sludge level alarm and controls start/stop of sludge rake. HART uploads data to DCS.

Nota: Not suitable for heavy steam or heavy floating oil conditions.

Caso 5: Building Materials Plant – Fly Ash Silo Solid Level Measurement

Configurazione: FMU90-R11CA131AA1A + FDU93 (35portata m)

Condizioni di lavoro: Dry fly ash silo with dust. Monitor silo level, high/low level alarm, control feeding and discharging belt conveyor.

Implementation Logic: Continuous solid level measurement. 3 relè: high level alarm, low level alarm, ultra-low level interlock to stop discharge. 4-20mA transmits level signal.

Limitazione: Ultrasonic wave attenuates severely under extremely high dust concentration. FMR radar transmitter is preferred.

Caso 6: Small Water Conservancy Channel – Irrigation Water Flow Monitoring

Configurazione: FMU90-R11CA131AA1A + FDU90

Condizioni di lavoro: Farm irrigation open channel with thin-plate weir. Outdoor wall-mounted installation, AC220V power supply.

Implementation Logic: Weir flow calculation and total irrigation water accumulation. Relay triggers alarm for too low / too high flow. IP66 housing withstands outdoor sunlight and rain.

Model Selection Guidelines for FMU90-R11CA131AA1A

✅ Adatto: Single sensor, pump alternation / rake control, 3 relay alarms, HART communication, AC power supply projects

❌Non adatto: Dual sensor measurement (select FMU90-R11CA231AA1A dual-channel version), heavy foam / dense steam / high dust applications

E+H FMU90-R11CA131AA1A (Prosonic S) Principio di funzionamento

FMU90 is manufactured by Endress+Hauser, not Pepperl+Fuchs. It is a remote ultrasonic level transmitter adopting Ultrasonic Time of Flight (ToF) principle. The complete system consists of FMU90 main unit + FDU series ultrasonic sensor.

Workflow:

1. Pulse Emission: FMU90 main unit drives FDU sensor via coaxial cable. Piezoelectric diaphragm vibrates and emits high-frequency ultrasonic pulses (typically tens of kHz), propagating vertically downwards to liquid or solid surface.
2. Echo Reflection: Sound wave hits medium surface and reflects. The same piezoelectric diaphragm receives the returned echo.
3. Tempistica & Sound Velocity Compensation: Main unit precisely records time difference between emission and reception. A temperature sensor integrated inside the sensor measures air temperature in real time to automatically compensate sound velocity (sound speed in air rises with temperature), eliminating temperature-induced measurement error.
4. Level Calculation: Actual liquid level L = sensor mounting height − measured distance D. Tank volume can be converted via tank linearization curve. For open channel weir / flume, built-in weir mathematical model calculates instantaneous flow and accumulated flow from liquid level directly.
5. Signal Processing (Echo Envelope + False Echo Suppression)

The main unit collects all echo signals to generate echo envelope curve, distinguishing real surface echo from false echoes caused by tank brackets, pipes and tank walls. False echo suppression can be configured in software to mask fixed interference objects and prevent mismeasurement.

Blanking Distance (B.D): Dead zone directly below sensor. The diaphragm residual vibration after pulse emission prevents echo reception, so this zone must be avoided during selection and installation.

2. Internal Signal & Output Logic of FMU90-R11CA131AA1A

Model configuration: Single sensor input, 3-channel SPDT passive relays, 1-channel 4~20mA HART, 90~253V AC power supply

1. Uscita analogica: 4~20mA+HART converts level / flow value to standard current signal for PLC/DCS. HART supports remote parameter reading, echo curve and diagnostic information access.
2. Relay Logic (3 SPDT relays for this model)

The main unit contains an arithmetic module. Besides level calculation, embedded control algorithm triggers relay action when liquid level reaches set threshold. It supports high/low level alarm, duty/standby pump alternation, sludge rake start/stop and flow over-limit alarm. No additional PLC programming for pump alternation; control can be realized locally inside transmitter.

3. Interfaccia uomo-macchina: Backlit display for local reading of level, echo envelope curve, alarm status and on-site menu configuration.
4. Extended Principle for Open Channel Flow Measurement

For Parshall flume, thin-plate weir and other open channel applications:

Only one FDU sensor is required to measure liquid level upstream of the weir.

FMU90 has built-in standard weir / flume mathematical models. Instantaneous flow is calculated from liquid level, and flow totalization is executed internally to accumulate total water volume. Relays can output flow alarms.

4. Key Limitations (Why it is not applicable for certain working conditions)
5. Foam, Vapore: Foam layer scatters and absorbs ultrasonic waves; steam changes air medium and attenuates sound wave, resulting in echo loss and measurement failure.
6. Polvere pesante: Dust particles absorb sound wave in solid silo applications. Echo intensity drops sharply, especially for long measuring range.
7. Medium independence: Ultrasonic measurement propagates in air. It is not affected by medium conductivity, density or dielectric constant, which is the main difference from radar level transmitters.