Ultrasonic Measurement For Level Gauge
An ultrasonic level transmitter is a non-contact instrument specialized in measuring liquids, slurries, and solid materials.
This product is suitable for corrosive or mildly corrosive liquids and substances, with a minimum range of 5 meters. Users can configure the measuring range independently; for instance, if the range is set to 1100 mm, the blind zone is approximately 400 mm. It supports a 4–20 mA DC electrical signal output and features an IP67 enclosure protection rating.
Key Features
- Non-contact media measurement, is not affected by the viscosity, specific gravity, etc. of the measured medium, and has strong anti-interference;
- Use environmentally friendly materials and do not pollute the measured medium;
- Non-toxic, can be used for pharmaceutical and food industry measurement;
- It can be equipped with relay contact output to realize the level alarm function;
- Panel button setting parameters, user parameter setting is convenient and fast;
- Using microprocessor and unique echo processing technology, it can adapt to the level and liquid level measurement under various complicated working conditions;
- With self-learning function, it can identify the true echo, and the measurement result is accurate. It has automatic temperature compensation, suppressing drift and improving measurement accuracy.
- The protection grade is IP67, which can be used in most outdoor working conditions.
Specifications
| Medium: | Liquid or material that is generally or slightly corroded; |
| Standard measuring range: | 5m, 10m, 15m, 30m, 50m, 60m; |
| Probe material: | ABS, PVDF, PTFE; |
| Transducer material: | Ceramic; |
| Measurement error: | 0.5%. 1.0%; |
| Accuracy: | ±3mm (no wave calm water surface) |
| Resolution: | 3~5mm or 0.1% (take large value） |
| Display mode: | LCD, parameters can be set through the panel buttons; |
| Signal output: | 4~20mADC; |
| Load resistance: | 250Ω (when two-wire 24V power supply); 500Ω (when four-wire 220VAC power supply); |
| Relay output: | 2 groups are optional, and the relay status is programmable; |
| Relay contact capacity: | 250VAC 8A. 30VDC 5A; |
| Process connection: | Thread: M60x2, G2″; Flange option: DN50-DN100 (other regulations can be customized) (HG/T 20592-2009); |
| Working temperature: | -25~80 °C; |
| Rated pressure: | -0.1 ~ 1.0MPa; |
| Communication interface: | RS232, RS485/Modbus, |
| Power supply: | Standard 24 V DC (two-wire system); Optional 220VAC (four-wire system); |
| Electrical interface: | M20*1.5, 1/2″NPT; |
| Explosion-proof grade: | ExiaIICT6Ga/ExdIICT6Gb; |
| Protection level: | IP67; |
| Shell material: | Engineering-plastics, aluminum alloy, SS304; |
| Ambient temperature: | (meter) -20-60 ° C; (sensor) -20~80 ° C; |
| Relative humidity: | 95%. |
Appliaction
An ultrasonic level meter fundamentally relies on “listening to echoes” to calculate distance: the probe emits sound waves that bounce off the liquid surface and reflect back, determining the liquid level height based on the time difference.
The ultrasonic level meter consists of an ultrasonic transducer (probe), which emits high-frequency pulsed sound waves. After the sound waves are reflected by the surface of the measured object (material), they are received by the transducer and converted into electrical signals. The propagation time of the sound waves is directly proportional to the distance from the probe to the object’s surface (i.e., the liquid level height).
Different probe materials dictate the chemical compatibility and environmental limits of the ultrasonic level meter. Below are the corresponding applications for ABS, PVDF, and PTFE:
1. ABS (Acrylonitrile Butadiene Styrene)
Applicable Industries: Water treatment, municipal engineering, environmental protection, and general light industry.
Working Conditions: Mildly corrosive or non-corrosive liquids, regular wastewater, clean water, and ambient temperatures (typically under 60°C to 70°C, non-pressure or low-pressure tanks).
Tank Types: Plastic tanks, open-top concrete pools, water storage tanks, and pump stations.
Environment: Indoor or sheltered outdoor environments with minimal exposure to harsh chemicals or extreme UV radiation.
2. PVDF (Polyvinylidene Fluoride)
Applicable Industries: Chemical processing, wastewater treatment, chemical storage, metallurgy, and electroplating.
Working Conditions: Moderately corrosive liquids (such as acids, alkalis, and salt solutions), chemical dosing systems, and environments requiring good mechanical strength and chemical resistance across broader temperature ranges.
Tank Types: FRP (Fiberglass Reinforced Plastic) tanks, plastic chemical storage tanks, and neutralization tanks.
Environment: Outdoor or industrial environments exposed to weathering, UV radiation, and chemical fumes.
3. PTFE (Polytetrafluoroethylene / Teflon)
Applicable Industries: Fine chemicals, pharmaceutical manufacturing, highly corrosive chemical production, and semiconductor industries.
Working Conditions: Highly corrosive or aggressive media (such as concentrated acids, strong alkalis, organic solvents, and strong oxidizing agents) that would degrade other plastics.
Tank Types: Lined steel tanks, specialized reaction kettles, and high-purity chemical storage containers.
Environment: Extremely harsh industrial environments with severe chemical vapor exposure and strict hygiene or chemical inertness requirements.
FAQ
What does "Measurement error: 0.5%, 1.0%" mean?
Accuracy Class / Error Range: This represents the maximum allowable error range between the measured value and the true value when the instrument operates under normal conditions.
Dual options or segmented accuracy:
0.5%: Represents higher accuracy. It usually corresponds to higher-end models, more rigorous calibration, or achieving an error within $\pm 0.5\%$ within a specific standard range.
1.0%: Represents standard industrial accuracy. It typically corresponds to standard models with a maximum allowable error of $\pm 1.0\%$.
Percentage of Full Scale (FS):
For example, for an ultrasonic level meter with a range of 5 meters, if the accuracy is 0.5%, the maximum absolute error across the entire range is: $5000\text{ mm} \times 0.5\% = \pm 25\text{ mm}$.
If the accuracy is 1.0%, the maximum absolute error is: $5000\text{ mm} \times 1.0\% = \pm 50\text{ mm}$.
Percentage of Reading: A few high-precision instruments calculate error based on the current actual reading, but for conventional level and pressure instruments, it is typically defaulted to Full Scale (FS).
Practical Significance in Model Selection:
0.5% High-Accuracy Version: Suitable for applications requiring more precise level control and material measurement (such as fine chemical dosing, high-value liquid storage tanks, and strict process monitoring).
1.0% Standard Version: Suitable for general industrial sites (such as ordinary sewage treatment pools, open water tanks, fire-fighting water reservoirs, or general ventilation and material storage), meeting daily monitoring needs with higher cost-effectiveness.
How to Calculate the Blind Zone of an Ultrasonic Level Meter
The blanking zone (or dead zone) of an ultrasonic level meter refers to a short distance right after the probe emits an ultrasonic pulse where the reflected echo cannot be effectively recognized by the receiving circuit due to acoustic reverberation and ringing effects. If the liquid level is measured within this blanking zone, the instrument will fail to read correctly or may even generate an error alarm.
1. What Determines the Size of the Blind Zone?
Hardware Design and Range: The size of the blind zone is primarily determined by the physical characteristics (frequency, power) and measuring range of the ultrasonic probe.
Short-range / Short-distance instruments (e.g., 5-meter range): The blind zone is typically smaller, generally around 0.3 meters to 0.5 meters (300 mm to 500 mm).
Long-range / Long-distance instruments (e.g., 10-meter, 20-meter range or above): Due to higher transmission power and longer ringing duration, the blind zone increases accordingly, potentially reaching 0.8 meters to 1.5 meters or even more.
2. How to Account for the Blind Zone During Installation and Calculation?
When calculating the installation height and maximum liquid level in practical applications, the following formulas must be strictly followed:
Core Principle: The highest liquid level (full level) inside the container must never enter the blind zone.
Calculation Example:
Suppose you purchase an ultrasonic level meter with a range of 5 meters and a blind zone of 400 mm (0.4 meters).
If the total height of the storage tank is 4.5 meters, the probe must be installed at least 4.5 meters away from the tank bottom, while ensuring that when material is filled to the maximum point, the liquid surface remains at least 400 mm away from the bottom of the probe.
If the liquid level exceeds this safety distance and enters the 400 mm blind zone, the instrument screen will typically display an error code (such as
E-01or loss-of-signal alarm).
3. Installation Troubleshooting Tips (How to Mitigate Blind Zone Effects)
Install an Extension Pipe / Raise the Mounting Base: If the top space of the container is limited and the maximum liquid level inevitably enters the blind zone, you can weld a short extension pipe to the top of the container to elevate the ultrasonic probe, ensuring that the physical distance from the probe face to the highest liquid level is greater than the blind zone value.
Parameter Compensation: Most modern ultrasonic level meters support manually entering the “probe installation height” or “blanking zone compensation value” in the instrument menu. While this optimizes signal processing to some extent, the physical blind zone itself cannot be completely eliminated by software.
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