The LONN-UL25 ultrasonic level meter provides continuous, non-contact liquid level measurement for water, oil, and chemical storage tanks. Using high-frequency pulse acoustic technology, it measures levels from 0 to 25 meters with ±0.25% accuracy. The integrated design combines transmitter, display, and RS485 communication in an IP65/IP68-rated housing, delivering 4–20mA analog output plus Modbus RTU digital interface. Ideal for industrial water treatment, petroleum storage, and chemical processing applications.
The LONN-UL25 represents LONNMETER’s advanced line of ultrasonic level sensors designed for continuous, non-contact liquid level measurement in industrial environments. Unlike traditional float-type or pressure-based level instruments that require direct contact with the process medium, the LONN-UL25 uses high-frequency pulse acoustic technology to measure liquid level from above, eliminating concerns about chemical compatibility, corrosion, and mechanical wear in the sensing element.
The measurement principle is straightforward: the ultrasonic transducer emits a high-frequency pulse that travels through the air above the liquid surface, reflects off the liquid, and returns to the sensor. The instrument measures the round-trip time and calculates the distance to the liquid surface using the speed of sound. This distance measurement is then converted to a level reading based on the configured tank height and zero-point settings. The non-contact design makes the LONN-UL25 water level sensor and oil level sensor ideal for corrosive chemicals, sanitary applications, and media where contact sensors would degrade or contaminate the process.
Available in five range configurations (5m, 10m, 15m, 20m, 25m), the LONN-UL25 covers applications from small process vessels to large bulk storage tanks and reservoirs. The integrated LCD display provides local readout of level or distance, while the 4–20mA analog output and RS485 Modbus RTU digital interface enable seamless integration with PLCs, SCADA systems, and DCS platforms. Built-in lightning protection ensures reliable operation in outdoor installations.
Range and Accuracy: The LONN-UL25 offers five measurement ranges to match tank dimensions and application requirements: 5m, 10m, 15m, 20m, and 25m. All models deliver ±0.25% to ±0.5% full-scale accuracy under standard conditions, sufficient for inventory management, process control, and overflow prevention applications. The 1mm resolution provides precise level indication for critical process monitoring.
Blind Zone Considerations: Every ultrasonic level sensor has a blind zone — the minimum distance from the transducer face where measurement is not possible due to ring-down effects. The LONN-UL25 blind zone ranges from 0.25m to 0.6m depending on the measurement range. During installation, ensure the sensor is mounted above the maximum liquid level plus the blind zone distance. For applications where this is not feasible, consult LONNMETER for guidance on minimizing blind zone impact.
Temperature Compensation: The speed of sound in air varies with temperature — approximately 0.17% per degree Celsius. The LONN-UL25 liquid level sensor incorporates built-in temperature compensation that continuously adjusts the speed-of-sound calculation based on ambient temperature, maintaining measurement accuracy across the -20°C to +60°C operating range without manual calibration adjustments.
| Parameter | Specification |
|---|---|
| Analog Output | 4–20mA current loop |
| Digital Output | RS485, Modbus RTU protocol (or customized protocol) |
| Update Rate | Real-time continuous |
| Resolution | 1mm |
The dual-output design provides flexibility for system integration. The 4–20mA analog signal connects directly to PLC analog input cards and legacy control systems, while the RS485 Modbus RTU digital interface enables high-resolution data transmission, remote configuration, and integration with modern SCADA and DCS platforms.
| Parameter | Specification |
|---|---|
| Protection Rating | IP65 / IP68 |
| Process Pressure | Below 4 atmospheres |
| Process Connection | G2 thread (standard); flange options available |
| Operating Temperature | -20°C to +60°C (high-temperature customization available) |
| Power Supply | DC12V / DC24V / AC220V |
| Lightning Protection | Built-in |
The IP65 protection rating ensures reliable operation in outdoor installations, washdown environments, and dusty industrial areas. The IP68 option provides submersion resistance for harsher conditions. The built-in lightning protection safeguards the electronics in outdoor installations prone to electrical storms. For more on ultrasonic measurement principles, see ISA’s process measurement standards.
The LONN-UL25 ultrasonic level sensor supports multiple installation methods to accommodate different tank configurations:
Flange Mounting: The standard G2 thread enables direct connection to tank nozzles or flange adapters. Flange mounting provides a robust mechanical connection for large tanks and high-vibration environments.
Bracket Installation: In open environments, bracket installation is commonly used, fixed with the instrument’s own flange or nut. Cut a circular hole slightly larger than the probe diameter (60mm) at the installation position, insert the instrument, and tighten the flange or nut from bottom to top.
Critical Installation Requirement: Installation must ensure that the probe surface of the instrument is level with the measured liquid surface. The probe front end should extend out from the mounting hole, not remain inside it.
Monitor water levels in storage tanks, reservoirs, wet wells, and clarifiers. The LONN-UL25 water level sensor provides the accuracy and reliability needed for pump control, overflow prevention, and inventory management in municipal and industrial water treatment facilities. The non-contact design eliminates fouling issues common with submerged level sensors in wastewater applications.
Measure liquid levels in diesel, gasoline, and fuel oil storage tanks. As an oil level sensor, the LONN-UL25 provides continuous level monitoring for inventory control, leak detection, and automated dispensing systems. The non-contact ultrasonic measurement principle eliminates sensor fouling and contamination concerns.
Monitor acid, base, solvent, and specialty chemical levels in process vessels and storage tanks. The non-contact ultrasonic measurement principle eliminates corrosion concerns associated with contact-type level sensors. The pressure rating below 4 atmospheres suits most atmospheric and low-pressure chemical storage applications.
Monitor cooling water, condensate, and process liquid levels in metallurgical plants and power generation facilities. The wide operating temperature range and robust protection rating ensure reliable operation in demanding industrial environments.
Measure ballast water, fuel oil, and liquid cargo levels in marine vessels and shipbuilding applications. The IP68 option and built-in lightning protection make the LONN-UL25 suitable for marine environments where moisture, salt spray, and electrical storms are common.
The LONN-UL25 ultrasonic level sensor operates on the time-of-flight principle:
Pulse Emission: The piezoelectric transducer converts electrical energy into a high-frequency acoustic pulse. This pulse propagates through the air above the liquid surface at the speed of sound (approximately 343 m/s at 20°C).
Reflection: When the acoustic pulse reaches the liquid surface, it reflects back toward the transducer. The liquid surface acts as an acoustic mirror due to the impedance mismatch between air and liquid.
Reception: The transducer receives the reflected echo and converts the acoustic energy back into an electrical signal. The instrument measures the time between pulse emission and echo reception.
Distance Calculation: Using the measured round-trip time and the speed of sound (adjusted for temperature), the instrument calculates the distance from the transducer face to the liquid surface: Distance = (Speed of Sound × Time) ÷ 2.
Level Conversion: The distance measurement is converted to liquid level based on the configured tank height and zero reference. The LCD display shows either the calculated liquid level or the distance from the probe to the liquid surface.
This non-contact measurement approach offers significant advantages: no moving parts, no chemical compatibility issues with the sensing element, minimal maintenance requirements, and suitability for a wide range of liquid types without changing the sensor.
Non-Contact Measurement: The ultrasonic principle eliminates direct sensor-liquid contact, avoiding corrosion, fouling, and contamination issues. Ideal for aggressive chemicals, sanitary applications, and media where contact sensors would degrade.
Wide Range Options: Five measurement ranges from 5m to 25m cover applications from small process vessels to large bulk storage tanks. Select the appropriate range based on tank height for optimal accuracy.
Dual Output — Analog and Digital: 4–20mA for legacy system integration, RS485 Modbus RTU for modern control systems. Both outputs can operate simultaneously for redundancy and flexibility.
Integrated LCD Display: Built-in display shows liquid level or space distance, enabling local monitoring and verification without external readout devices.
Built-in Lightning Protection: Safeguards electronics in outdoor installations exposed to electrical storms, enhancing reliability and reducing maintenance costs.
Robust Protection: IP65 standard rating for outdoor and washdown environments; IP68 option for submersion resistance in harsher conditions.
Flexible Power Options: DC12V, DC24V, or AC220V power supply options accommodate different installation environments and power availability.
Q1: What measurement ranges are available for the LONN-UL25?
The LONN-UL25 offers five measurement ranges: 5m, 10m, 15m, 20m, and 25m. Select the range based on your maximum tank height. All ranges deliver ±0.25% – 0.5% accuracy and 1mm resolution. Custom ranges are available upon request.
Q2: What is the blind zone and how does it affect installation?
The blind zone ranges from 0.25m to 0.6m depending on the measurement range — this is the minimum distance from the transducer face where measurement is not possible. Mount the sensor above the highest liquid level plus the blind zone distance. For example, with a 10m range model (0.4m blind zone), mount the sensor at least 0.4m above the maximum liquid level.
Q3: Can the LONN-UL25 measure oil and petroleum products?
Yes. The LONN-UL25 oil level sensor is designed for petroleum and fuel oil applications. The non-contact measurement principle eliminates concerns about sensor fouling or contamination from hydrocarbons. For hazardous area applications, consult LONNMETER for appropriate explosion-proof options.
Q4: What outputs does the LONN-UL25 provide?
The LONN-UL25 provides two output types: 4–20mA analog current loop (compatible with PLCs and control systems) and RS485 Modbus RTU digital communication (for SCADA/DCS integration). Both outputs can operate simultaneously.
Q5: What power supply options are available?
The LONN-UL25 supports three power supply options: DC12V, DC24V, and AC220V. Choose based on your facility’s power infrastructure. All versions include built-in lightning protection for outdoor installations.
Q6: What is the maximum process pressure?
The LONN-UL25 is rated for process pressures below 4 atmospheres. This suits most atmospheric storage tanks and low-pressure process vessels. For higher-pressure applications, consult LONNMETER for alternative solutions.
Q7: What industries does the LONN-UL25 serve?
The LONN-UL25 serves petroleum, chemical, coal chemical, metallurgy, power, shipping, medicine, grain, textile, brewing, aerospace, military, and fire protection industries. The non-contact ultrasonic principle makes it suitable for most liquids that reflect acoustic energy.
LONN-UL25 Ultrasonic Level Meter
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