Siemens 7ML5110-1GD07-4AF3 Ultrasonic Level Gauge for Non-Contact Level Measurement

The Siemens 7ML5110-1GD07-4AF3 is an ultrasonic level transmitter from the Sitrans Probe LU family. It uses ultrasonic sound waves to measure distance to liquid or solid surfaces without contact, making it suitable for corrosive, sticky, or dirty media. The device outputs a 4-20 mA analog signal proportional to level or volume, integrating directly with PLC analog input cards. It is commonly used in water treatment, chemical storage, and bulk solids handling.

Measurement Specifications

Measurement principle: Ultrasonic pulse echo (time of flight). Operating frequency: 30 kHz. Measurement range: 0.25m to 8m (0.8 to 26 ft) for liquids; up to 4m for solids (with angle of repose compensation). Dead band: 0.25m (cannot measure closer). Accuracy: ±0.15% of range or ±3mm, whichever greater. Resolution: 1mm. Temperature compensation: Built-in sensor for automatic sound velocity correction. Response time: Adjustable from 1 to 60 seconds. The gauge can measure level, distance, volume, or open channel flow.

Output and Communication

Analog output: 4-20 mA (isolated, loop-powered or externally powered), scalable over any part of the measurement range. The output is HART compatible, allowing digital communication with a handheld communicator or HART-enabled PLC modules. Additionally, the device includes two programmable relay outputs (SPDT, 5A at 250V AC) for pump control, high/low alarms, or fault indication. An optional RS-485 Modbus RTU interface is available.

Electrical and Power

Power supply: 24V DC (20-36V DC) nominal. Current consumption: 30mA (without loop load). The 4-20mA loop can be sourced from the same supply (2-wire) or separate (4-wire). For 2-wire operation, the total loop load must be ≤600 Ω. For 4-wire, the device can drive loads up to 1000 Ω. The internal power supply provides surge protection and reverse polarity protection. EMI filtering meets EN 61326-1 industrial levels.

Transducer and Housing

The transducer is encapsulated in PVDF (polyvinylidene fluoride) with a 2-inch NPT mounting thread. The transducer face is designed to self-drain and resist buildup. Maximum pressure: 0.5 bar (7.25 psi) absolute. The housing is die-cast aluminum with an epoxy coating, rated IP67/NEMA 4X. An integral sun shield is available as an accessory. The transducer cable is permanently attached (5m standard) and can be extended up to 365m. The unit includes a local LCD display with backlight showing level, distance, or volume.

Configuration and Programming

The device can be configured via the three-button local interface (programming keypad) with a menu-driven display. Parameters include range, units (m, ft, %, volume), output scaling, damping time, and echo confidence thresholds. Advanced features include false echo suppression to ignore fixed obstacles. The device can be programmed with up to 10 points for volume/level linearization (e.g., odd-shaped tanks). For complex setups, Siemens SIMATIC PDM software or a HART handheld communicator can be used.

Environmental Ratings

Operating temperature: -40°C to 80°C (transducer); -20°C to 60°C (electronics). Storage: -40°C to 85°C. Humidity: 0-100% (outdoor use). The gauge is suitable for outdoor installation with direct sunlight and rain. It is also rated for use in hazardous locations (ATEX/IECEx Ex nA IIC T4, non-incendive). The housing has a drain hole to prevent condensation. Vibration resistance: 1g at 10-500Hz.

Applications

Typical applications include: Storage tank level monitoring (water, wastewater, chemicals), sump level control, pump station lift stations, open channel flow measurement (with a flume), and bulk solids level in hoppers and silos (up to 4m). The non-contact measurement avoids maintenance issues with mechanical floats, capacitance probes, or pressure transmitters that can clog or corrode.

Installation Guidelines

The transducer must be mounted perpendicular to the material surface. Avoid mounting near tank walls (minimum 0.5m from side). For solids, use an offset mounting to reduce false echoes. For conical bottom tanks, use a stilling well or adjust the dead band. The transducer face must be free from ice, condensation, or heavy dust; a heater or purging system may be required. Use twisted shielded cable for 4-20mA run to the PLC, terminated properly to avoid ground loops.

Maintenance and Calibration

Periodically clean the transducer face with a soft cloth. No routine recalibration is required under normal conditions; the device uses factory calibration traceable to international standards. However, field verification can be performed by measuring an empty tank distance or using the simulation mode. The onboard echo profiling can be used to diagnose installation problems. Firmware upgrades are possible via HART modem and PC.

Conclusion

The Siemens 7ML5110-1GD07-4AF3 ultrasonic level gauge provides reliable, non-contact level measurement for industrial processes. Its 4-20 mA output with HART and relay outputs simplify integration with PLC-based control systems, making it a preferred choice for level monitoring applications.