How to choose a suitable ultrasonic level gauge? Five core points to help you make accurate decisions

In the fields of industrial production, water conservancy monitoring, environmental protection treatment, etc., liquid level measurement is a key link to ensure stable and safe operation of processes. Ultrasonic level gauges have become the preferred equipment for many scenarios due to their advantages of non-contact measurement, convenient installation, and low maintenance costs. However, there are many types of ultrasonic level gauges on the market with large parameter differences. If not selected properly, problems such as large measurement errors, rapid equipment damage, and even inability to function properly may occur. This article will start from five core points and teach you step by step to select the ultrasonic level gauge that is most suitable for practical needs.

1、 First, clarify the measurement requirements: accurately match the range and accuracy to avoid "excessive selection" or "insufficient capability"

The first step in choosing an ultrasonic level gauge is to clearly define its own measurement needs - this directly determines the core performance parameters of the equipment and is also the key to avoiding cost waste or functional deficiencies.

1. Range: Reserve a safety margin to avoid "measurement blind spots"

Ultrasonic level gauges have "blind spots" (areas below the probe that cannot be accurately measured, usually 0.2-1 meters, depending on the model), so in actual selection,The measuring range should cover the "maximum liquid level height+blind spot distance", and an additional 10% -20% safety margin should be reserved.

For example, a certain chemical storage tank needs to measure a liquid level of 0-5 meters. If the selected equipment has a blind spot of 0.5 meters, the theoretical range should be at least 5.5 meters. In practice, it is recommended to choose models with a range of 0-6 meters or 0-7 meters - which can avoid entering the blind spot when the liquid level reaches the upper X and also cope with sudden liquid level fluctuations.

On the contrary, if only the liquid level of 0-2 meters needs to be measured in practice, but equipment with a range of 0-10 meters is chosen, the measurement accuracy will decrease when the liquid level changes in a small range due to the large range, which belongs to "excessive selection".

2. Accuracy level: Choose as needed, balance "accuracy requirements" and "cost budget"

The accuracy level of ultrasonic level gauges is usually expressed as "full scale percentage (FS)", with common specifications including ± 0.1% FS, ± 0.2% FS, and ± 0.5% FS. The higher the accuracy, the higher the equipment cost, and it is necessary to choose reasonably according to the importance of the scene:

High precision demand scenarioFor food ingredient tanks, pharmaceutical reaction vessels, precision chemical metering, etc., precise liquid level control is required to ensure product quality, and models with ± 0.1% - ± 0.2% FS should be selected;

Conventional monitoring scenariosFor liquid level monitoring in ordinary industrial storage tanks and sewage regulating tanks, only a rough understanding of liquid level changes is needed, and an accuracy of ± 0.5% FS can meet the requirements, without the need to pursue high accuracy and waste costs.

2、 Understanding the characteristics of the medium: targeted solutions to the interference between "liquid type" and "liquid level state"

The characteristics of the measured liquid are the core factors affecting the measurement stability of the ultrasonic level gauge - the physical state (cleanliness, corrosivity) and liquid level morphology (calm/fluctuation/with foam) of different liquids have different requirements on the probe material and signal processing capability of the equipment.

1. Liquid type: Select the appropriate probe material from "cleanliness" and "corrosiveness"

Clean liquids (water, alcohol, cooking oil, etc.)The liquid is free of impurities and corrosion, and a standard level gauge with ordinary ABS or PVC material probes can be selected for high cost-effectiveness;

Cloudy/bubbly liquids (mud, sewage, fermentation broth, etc.)This type of liquid is prone to scattering ultrasonic signals, resulting in weakened echoes. Suggested choiceHigh frequency probe (such as 200kHz or above)Or models with "signal filtering function" have stronger penetration of high-frequency signals, and the filtering function can filter out clutter and improve measurement stability;

Highly corrosive liquids (acid-base solutions, chemical solvents, etc.)Attention should be paid to the anti-corrosion performance of the probe, and the material should be selected from PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride) or Hastelloy alloy with strong corrosion resistance. At the same time, ensure that the equipment casing also has anti-corrosion ability to avoid long-term contact and corrosion.

2. Liquid level status: deal with the interference of "fluctuation, foam and steam"

Calm liquid level (such as static water storage tank)No special interference, regular models can work normally;

Fluctuating liquid level (such as mixing tanks, storage tanks near pump bodies)Severe fluctuations in liquid level can cause unstable echo signals and large fluctuations in measurement data. There are two possible solutions: one is to chooseParabolic focusing probeFocusing on ultrasonic signals to reduce signal dispersion caused by fluctuations; The second is to choose models with built-in "liquid level averaging algorithm" and calculate the average liquid level over a period of time through software to weaken the impact of fluctuations;

With foam/steam liquid level (such as beer fermentation tank and boiler water tank): foam will absorb ultrasonic signal, and steam will interfere with signal transmission, resulting in "false liquid level" or "no echo". Suggest priority selectionLow frequency probe (e.g. 20-50kHz)The low-frequency signal penetration is stronger and can penetrate the thin foam layer; If the foam is thick, it can be installed with "waveguide tube". Place the probe in the waveguide tube to avoid the direct interference of foam and steam and ensure the signal stability.

3、 Consider environmental factors: temperature, pressure, humidity, none of which can be ignored

The working environment of ultrasonic level gauges (temperature, pressure, humidity, corrosiveness) directly affects the service life and measurement stability of the equipment, and the appropriate protection level and special design model should be selected according to the actual environment.

1. Temperature and pressure: Avoid equipment damage caused by exceeding the range

temperatureThe working temperature range of conventional ultrasonic level gauges is -20 ℃ -75 ℃. If applied to high-temperature scenarios (such as high-temperature asphalt tanks and steam storage tanks), a "high-temperature type" level gauge should be selected. Some specialized models can withstand temperatures of 150 ℃ or even higher (note: in high-temperature environments, the probe material and electronic components need to withstand high temperatures synchronously to avoid local overheating failure);

pressureMost ultrasonic level gauges are suitable for atmospheric pressure environments (-0.1MPa-0.1MPa). If used in high-pressure scenarios (such as high-pressure reactors, pressure storage tanks), "high-pressure" products should be selected. The probe and housing of such equipment are specially sealed and designed to withstand pressures above 0.6MPa (specific needs to be confirmed based on actual pressure values) to avoid equipment leakage or damage caused by excessive pressure.

2. Humidity and corrosiveness: Improve protection level and extend service life

humidityHigh humidity environments (such as aquaculture ponds and sewage treatment plants) can easily cause internal moisture and short circuit faults in equipment. Choose models with high protection levels, represented by IP codes, commonly IP65 (dustproof, anti spray water), IP67 (dustproof, short-term immersion), IP68 (dustproof, long-term immersion). Generally, IP67 or above is selected for high humidity scenarios. If underwater installation is required (such as open channel liquid level measurement), IP68 should be selected;

Strong corrosive environment (such as chemical workshops, near acid pickling tanks)In addition to the anti-corrosion material of the probe, the overall casing of the equipment also needs to have anti-corrosion capabilities. Stainless steel casing (such as 316L) can be selected, and anti-corrosion treatment should be carried out on the interface, cables and other details to avoid long-term exposure to corrosive gases or liquids.

4、 Choose the right installation method: avoid obstacles, adapt to the space, and ensure normal signal

Improper installation is a common reason for inaccurate measurement of ultrasonic level gauges - if the probe is obstructed by obstacles, not perpendicular to the liquid level, or if there is insufficient installation space, it will affect the transmission and reception of ultrasonic waves.

1. Avoid obstacles and ensure "unobstructed"

The installation position of the probe needs to meet two core requirements: firstlyUnobstructed obstructionAvoid equipment such as ladders, brackets, pump valves, and feed pipes to prevent ultrasonic signals from being reflected by obstacles, which can lead to "misjudgment of liquid level"; SecondThe probe is perpendicular to the measured liquid levelTilting installation can cause the echo signal to deviate from the probe, making it unable to be effectively received and increasing measurement errors.

At the same time, it is necessary to ensure that the distance from the bottom of the probe to the low liquid level of z is greater than the blind zone of the equipment, in order to avoid the low liquid level of z entering the blind zone and causing measurement failure.

2. Suitable installation space: split vs integrated, flange vs thread

Installation spaceIf the installation location is narrow (such as on the top of a small storage tank or inside a pipeline), the integrated level gauge (probe and electronic part integrated) may not be able to be installed due to its large volume. In this case, the "split type" model can be selected - the smaller probe is installed in a narrow space, and the electronic part (display screen, wiring terminal) is installed in a nearby location for easy operation. The two are connected by cables (cable length can generally be customized, up to 100 meters);

connection methodCommon installation and connection methods include flange connection and threaded connection. Flange connection is suitable for large-diameter storage tanks and high-pressure scenarios, with stronger sealing and stability; Threaded connections are suitable for small-diameter storage tanks and atmospheric pressure scenarios, and are easy to install. The matching connection method should be selected based on the size of the tank opening (such as flange specifications, thread models) to avoid "inability to install" or "inadequate sealing".

5、 Pay attention to output and compatibility: ensure that "data can be transmitted and the system can be connected"

The core function of ultrasonic level gauge is to transmit measurement data to monitoring systems (such as PLC, DCS, upper computer). If the output mode or communication protocol is incompatible, it will lead to "data islands" and cannot achieve remote monitoring and automation control.

1. Output method: Match existing collection device interfaces

There are two common output methods:

4-20mA analog outputSuitable for simple liquid level display or control, stable signal transmission, strong anti-interference ability, most PLCs and digital displays support 4-20mA input, with wide compatibility;

RS485 digital outputSuitable for scenarios that require the transmission of large amounts of data (such as real-time liquid level, historical data, equipment status), it can achieve multi device networking and has a long transmission distance (up to 1200 meters). If the existing system uses PLC or upper computer for data acquisition, it is necessary to confirm whether the input interface of the acquisition device supports RS485 to avoid interface mismatch.

2. Communication protocol: Ensure "data interoperability"

Communication protocol is the "language" between devices and systems. If the protocol does not match, data cannot be parsed properly. The commonly used protocols in the industrial field currently include Modbus and Hart

Modbus protocolWidely applicable, almost all PLC and SCADA systems support it, with strong compatibility, suitable for most industrial scenarios;

Hart protocolMainly used for intelligent instruments, it can achieve "two-way communication" (both transmitting measurement data and remotely setting device parameters), suitable for scenarios that require remote debugging and monitoring.

When selecting, it is necessary to clarify the communication protocols supported by the existing system and choose the corresponding level gauge model to avoid data transmission failure due to protocol incompatibility.

Conclusion: There is no shortcut to selection, "matching on demand" is the key

Choosing an ultrasonic level gauge, there is no "best" option, only "z is suitable". Whether it is range, accuracy, medium adaptation, environmental protection, installation method, or system compatibility, the core logic is to "start from actual needs" - first clarify one's own measurement scenario, medium characteristics, environmental conditions, and system requirements, and then screen them one by one against the five key points in order to avoid selection errors and select an ultrasonic level gauge with accurate measurement, stability, durability, and high cost-effectiveness, to safeguard the safe and efficient operation of the production process.