Ultrasonic level gauge is a non-contact instrument based on the principle of ultrasonic reflection to measure liquid level. It has the advantages of easy installation, simple maintenance, and is not affected by the corrosiveness of the medium. It is widely used in industries such as chemical, water conservancy, food, and environmental protection. Scientific selection directly determines measurement accuracy, stability, and service life. The following provides a detailed explanation from the core dimensions.
The primary prerequisite for selection is to clarify the core requirements for on-site measurement, which is the foundation for all subsequent choices.
Determine the low and high values of Z for liquid level measurement, reserve 10% -20% redundant range to avoid measurement failure under extreme working conditions.
The conventional ultrasonic level gauge covers a range of 0.1m-30m, with a small range (0.1m-5m) suitable for small storage tanks and material tanks, and a large range (10m-30m) suitable for large reservoirs and chemical storage tanks.
Note that the larger the range, the better. Choosing beyond the range will lead to a decrease in measurement accuracy and increase unnecessary costs.
Pay attention to whether the liquid medium has corrosive, volatile, foam, suspended solids, temperature, pressure and other parameters.
Corrosive media do not require special treatment (non-contact ultrasonic measurement), but sensor probes made of corrosion-resistant materials need to be selected; The medium containing a large amount of foam or suspended solids will absorb ultrasonic waves, so the model with foam compensation function shall be selected.
High temperature media (over 80 ℃) should be selected as high-temperature specific types, equipped with cooling devices or high-temperature adaptation probes; Under high pressure conditions (exceeding 0.3MPa), it is necessary to confirm the pressure resistance level of the instrument to avoid probe damage.
Solid media (such as powders and particles) should be selected with specialized models for solid measurement, which have smaller sound wave diffusion angles and stronger reflection signal recognition capabilities.
Determine the accuracy level according to industry requirements. For conventional industrial scenarios, an accuracy of ± 0.5% FS is sufficient, while for metrological scenarios, models with an accuracy of ± 0.2% FS or higher should be selected.
Accuracy is related to the range, and the smaller the range, the easier it is to ensure accuracy; When conducting large-scale measurements, it is necessary to prioritize the selection of high-precision chips and advanced signal processing technology products.
The on-site environment directly affects the transmission of ultrasonic signals and requires targeted selection based on installation conditions.
The installation position should avoid obstacles such as tank walls, mixers, pipelines, etc. The distance between obstacles and probes should be greater than the sound wave diffusion radius (usually 1/10 of the range).
When installing at the top, the vertical distance between the probe and the liquid level should be within the range, and the diameter of the installation hole should match the size of the probe; Side mounted is suitable for scenarios with limited headspace, but it is necessary to ensure that the probe is not submerged by the medium.
For narrow spaces or complex tank types (such as irregular tanks and horizontal tanks), small-sized probes or split type instruments should be selected. The split type can separate the transmitter and probe for installation, flexibly adapting to the installation space.
The ambient temperature range should match the working temperature of the instrument. The working temperature of conventional models is -20 ℃ -60 ℃. For low temperature environments (below -20 ℃), a low-temperature antifreeze type should be selected, and for high temperature environments, a heat dissipation device should be used.
Products with a protection level of IP65 or above should be selected for high humidity and dusty environments, and additional sun protection and rain covers should be provided for outdoor installation.
Avoid installing near strong electromagnetic interference (such as frequency converters and high-power motors). If it is impossible to avoid, choose a model with anti-interference design or use shielded cable wiring.
Open containers can be of ordinary type; It is necessary to confirm whether there is pressure and steam inside the sealed container, and choose a special type for sealed containers. Some models need to be equipped with waveguide tubes for auxiliary measurement to ensure signal stability.
Under stirring conditions, instruments with stirring compensation function should be selected, or the installation position should be adjusted to avoid the liquid level vortex generated by stirring, which can cause signal reflection disorder.
Based on actual application requirements, screen the functional configuration and performance indicators of the instrument to avoid functional redundancy or missing.
The conventional output signals include 4-20mA analog output and relay switch output, which meet the access requirements of most industrial control systems.
When remote monitoring or data uploading is required, choose models with communication interfaces such as RS485 (Modbus protocol), HART, Profibus, etc., to facilitate integration with PLC and DCS systems.
Special scenarios (such as explosion-proof areas) require confirmation of the explosion-proof level of the output signal, which is consistent with the on-site explosion-proof requirements.
Explosion proof areas (such as chemical workshops and oil and gas storage tank areas) must use explosion-proof ultrasonic level gauges, and the explosion-proof level must comply with the on-site hazardous area classification (such as Ex ia IIC T6, Ex d IIB T4, etc.).
The protection level Z is as low as IP65. It is recommended to choose IP67 or above for outdoor, humid or dusty environments to prevent moisture and dust from entering the instrument and causing malfunctions.
Scenarios with large liquid level fluctuations (such as rivers and reaction vessels) require the selection of models with dynamic tracking algorithms to improve signal stability;
For scenarios that require liquid level alarm and automatic control, select models with relay output and set high and low liquid level alarm thresholds;
In long-distance transmission scenarios, the signal transmission distance needs to be confirmed. Analog output usually supports transmission within 1000m, while digital signals can extend the transmission distance through the bus.
High quality brand and comprehensive after-sales service are the guarantees for the long-term stable operation of instruments.
Priority should be given to brands with good market reputation and mature technology, whose products have been verified in the long-term market and have more reliable quality.
Domestic and foreign brands have their own advantages: international brands such as Siemens and E+H have advanced technology and high precision, suitable for G-end scenarios; Domestic brands such as Rosemount and Cologne have high cost-effectiveness and strong adaptability, meeting conventional industrial needs.
Confirm whether the supplier provides installation guidance, debugging training, and other services. Professional installation and debugging under complex working conditions can significantly improve measurement effectiveness.
Pay attention to the duration of the warranty period (usually 1-2 years), as well as whether there are convenient maintenance channels and fast spare parts supply to avoid long-term inability to restore use after a malfunction.
Avoid using ultrasonic level gauges in a vacuum environment, as ultrasonic waves cannot propagate in a vacuum;
When measuring volatile media, it is necessary to confirm whether the medium vapor will condense on the probe, and if necessary, choose a probe with anti condensation function;
Regularly calibrate instruments, especially when there are changes in medium characteristics and environmental conditions, to ensure measurement accuracy.
Blindly pursuing a large range: a range that is too large not only increases costs, but also reduces measurement accuracy. Therefore, the appropriate range should be selected according to actual needs;
Neglecting environmental interference during installation: Failure to avoid obstacles, electromagnetic interference, and other factors leads to signal loss and inaccurate measurements;
Confusion of explosion-proof levels: Using non explosion-proof instruments in explosion-proof areas poses a safety hazard.
The selection of ultrasonic level gauges requires a comprehensive consideration of measurement requirements, on-site environment, functional configuration, and other factors. The core is "adaptability" - to accurately match the performance parameters of the instrument with actual working conditions. Before selecting, it is recommended to communicate fully with the supplier, provide detailed on-site parameters, and have professional technicians assist in recommending suitable models to avoid measurement errors or equipment failures caused by improper selection.