Ultrasonic level meters are non-contact devices that use ultrasonic wave reflection principles for level measurement. They offer advantages such as easy installation, simple maintenance, and resistance to medium corrosion, making them widely used in industries like chemical, water management, food processing, and environmental protection. The accuracy of the selection directly affects measurement precision, stability, and service life. This guide covers the essential factors for choosing the right ultrasonic level meter.
1. Clarify Measurement Parameters
The first step in selection is to clearly define the key measurement requirements for the site. This will serve as the basis for all subsequent decisions.
Measurement Range
The first consideration is determining the minimum and maximum measurement values, with a 10% to 20% margin to avoid measurement limitations in extreme conditions. Typical ultrasonic level meters cover ranges from 0.1m to 30m. Small ranges (0.1m-5m) are suitable for small tanks or hoppers, while larger ranges (10m-30m) are suitable for large reservoirs or chemical storage tanks. Remember, a larger range does not always equate to better performance; choosing an excessive range can reduce accuracy and unnecessarily increase costs.Medium Characteristics
The medium being measured must be considered, especially regarding its corrosiveness, volatility, foam, and suspended solids, as well as temperature and pressure conditions.Corrosive media do not require special treatment, but the sensor probe must be made from corrosion-resistant materials.
Media with foam or suspended solids will absorb ultrasonic waves and require a model with foam compensation capabilities.
High-temperature media (above 80°C) necessitate a high-temperature model with cooling or specially adapted probes.
For high-pressure conditions (over 0.3MPa), ensure the instrument’s pressure resistance rating is adequate.
For solid media (e.g., powders, particles), select a model designed for solid measurement, with a narrower ultrasonic beam angle for stronger signal reflection.
Accuracy Requirements
The accuracy level should be defined based on the industry requirements. Standard industrial applications typically require accuracy of ±0.5% FS, while metering-level applications require models with ±0.2% FS or better. Accuracy correlates with range: smaller ranges generally ensure better accuracy, while longer ranges necessitate high-precision chips and advanced signal processing technologies.
2. Adaptation to Installation Environment
The installation environment significantly impacts the ultrasonic signal’s transmission, and selecting the right device should be based on these conditions.
Installation Space and Methods
Ensure that the installation location avoids obstructions such as tank walls, mixers, or pipelines, maintaining a distance greater than the ultrasonic beam spread radius (usually 1/10th of the range). When installing on top, ensure the probe’s vertical distance is within the measurement range, and the installation hole diameter matches the probe size. For side-mounted installations (in spaces with limited headroom), ensure the probe is not submerged in the medium.In confined spaces or complex tank shapes (e.g., spherical or horizontal tanks), consider using a small-sized probe or split-type devices, where the transmitter and probe can be installed separately, allowing greater flexibility in installation.
Environmental Conditions and Interference
The temperature range of the device should match the operating environment, with typical models supporting -20°C to 60°C. For low-temperature environments below -20°C, choose a freeze-resistant model, and for high temperatures, ensure adequate heat dissipation mechanisms are in place.In high-humidity or dusty environments, select devices with an IP65 or higher protection rating. For outdoor installations, use additional protective covers against sun or rain exposure. Avoid installations near strong electromagnetic interference (such as frequency converters or large motors). If this is unavoidable, choose models with anti-interference features or use shielded cables.
Container Structure Characteristics
For open containers, regular models are sufficient. For sealed containers, verify whether there is internal pressure or steam, and select a model designed for sealed containers. Some models may require the use of a guided wave pipe to stabilize the signal. In agitated conditions, choose models with agitation compensation functions or adjust installation locations to avoid turbulence that can disrupt signal reflection.
3. Core Functions and Performance Parameters
Choose an ultrasonic level meter based on its features and performance parameters tailored to the specific application. Avoid overloading with unnecessary features or leaving out essential ones.
Signal Output and Communication Interfaces
Common output signals include 4-20mA analog output and relay switch output, sufficient for most industrial control systems. For remote monitoring or data upload, select models with communication interfaces such as RS485 (Modbus protocol), HART, or Profibus for easy integration with PLC or DCS systems. In explosive areas, verify the device’s explosion-proof rating to match on-site safety requirements.Explosion-Proof and Protection Ratings
In hazardous areas (e.g., chemical plants or oil and gas storage), explosion-proof ultrasonic level meters are a must. The explosion-proof rating must meet local area classifications (e.g., Ex ia IIC T6, Ex d IIB T4). The protection rating should be at least IP65, with IP67 or higher preferred for outdoor, damp, or dusty environments to prevent water and dust ingress.Special Function Requirements
In scenarios with fluctuating liquid levels (e.g., rivers or reactors), choose models with dynamic tracking algorithms for better signal stability. For applications requiring level alarms or automatic control, opt for models with relay outputs that can set high and low-level thresholds. In cases requiring long-distance transmission, confirm the signal transmission distance. Analog signals typically support transmission up to 1000 meters, while digital signals can extend further via bus systems.
4. Brand and After-Sales Considerations
Reliable brands and robust after-sales service ensure the long-term stability of the device.
Brand Selection
Choose brands with a good market reputation and mature technology. These products have been validated over time, ensuring higher reliability.After-Sales Service
Confirm whether the supplier provides installation guidance, commissioning, and training services. Professional support during installation and commissioning greatly enhances measurement accuracy, especially in complex environments. Pay attention to the warranty period (typically 1-2 years) and ensure there are convenient repair channels and quick spare part availability to minimize downtime in case of failures.
5. Common Selection Pitfalls
Important Considerations
Avoid using ultrasonic level meters in vacuum environments, as ultrasonic waves cannot travel in a vacuum. When measuring volatile media, verify whether vapor may condense on the probe; choose models with anti-condensation features if necessary. Periodically calibrate the instrument, especially if there are changes in medium characteristics or environmental conditions to maintain measurement accuracy.Common Mistakes
Do not blindly pursue large measurement ranges. Excessive range increases costs and decreases accuracy. Choose a range that fits the actual measurement needs. Avoid overlooking environmental interference such as obstructions or electromagnetic noise, which can cause signal loss and inaccuracies. Never confuse explosion-proof ratings; using non-explosion-proof devices in hazardous areas poses safety risks.
Ultrasonic level meter selection involves a comprehensive evaluation of measurement needs, site conditions, functionality, and performance. The key to success is ensuring that the meter’s parameters align perfectly with the actual working conditions. Prior to selecting a model, it’s recommended to have in-depth discussions with suppliers and provide detailed site specifications, allowing professional technicians to assist in recommending the most suitable model and avoiding issues like measurement errors or device malfunctions.