Ultrasonic Level Transmitter: Installation, Maintenance, Application

An ultrasonic level sensor is a remarkable tool used for measuring the level of target solids and liquids in an industrial environment. Today, this post guides you to know this level measurement with detailed descriptions and walks you through how to install it for measuring different targets.

What is an ultrasonic level transmitter?

An ultrasonic level transmitter is a highly effective device designed to measure the level of liquids, solids, or slurries in tanks, silos, and other containers. It leverages ultrasonic waves with high-frequency sound waves ranging from 20 kHz to 200 kHz that are beyond human hearing to provide accurate level readings.

This non-contact measurement technology is widely used across industries for its reliability and versatility.

How does an ultrasonic level transmitter work?

To complete a precise measurement, its components cooperate tidily and organizedly inside its casing body:

1. Emission of Ultrasonic Waves: The transmitter sends a burst of ultrasonic waves downward from a transducer toward the material's surface.

2. Echo Detection: These waves reflect off the surface and return to the transducer, which serves as both a sender and receiver.

3. Time-of-Flight Calculation: The device measures the time taken for the echo to return. Using the speed of sound in air (approximately 343 m/s at 20°C, adjusted for temperature, humidity, and pressure), the distance is calculated with the formula:

Note: The division by 2 accounts for the round trip of the wave.

4. Level Determination: The level is derived by subtracting the measured distance from the known distance between the transducer and the container's bottom.

5. Transducer: Converts electrical signals into ultrasonic waves and captures the returning echoes.

6. Electronics Unit: Processes data, applies environmental corrections, and converts it into a readable level measurement.

7. Display/Output: Features a digital display or outputs a signal (e.g., 4-20 mA) for integration with control systems.

How to install an ultrasonic level transmitter?

Installing an ultrasonic level transmitter correctly is crucial for accurate measurements of liquids, solids, or slurries in tanks, silos, and wells. These non-contact devices rely on proper positioning to avoid false echoes and ensure reliable performance.

Based on the changes of the measured targets and working scenarios, the approaches and tips for the ultrasonic level measurement installations vary. Just take the following details as references for the final installation:

Before the installation:

Before exploring every essence of installation, here are some tips that need to be taken into consideration to enhance safety and accuracy:

• Choose threaded or flange mounting based on your container type.
• Install in well-ventilated areas to prevent overheating.
• Avoid direct sunlight, temperatures above 60°C, humidity over 85%, electromagnetic interference, vibrations, condensation, or environments with dust, steam, or corrosive gases.
• Ensure the probe's emitting surface is perpendicular to the measured surface where possible.
• Maintain a minimum distance (blind area) from the medium—typically 0.35m, but it may increase with extensions.
• Use tools like universal flanges for alignment in challenging setups.

Installing ultrasonic level sensors for measuring liquids

Ultrasonic transmitters excel in liquid level monitoring. Here's how to install them in various tank configurations:

1. Flat-Top Tanks

1. Short Nozzle Installation: For nozzles ≤60mm long and ≥100mm inner diameter with flat, burr-free walls, position the probe so its emitting surface extends 3cm below the flange bottom. This minimizes interference.
2. Direct Mounting Without Nozzle: Open a circular hole on the tank top and secure with a flange or universal joint. The probe should sit below the reference plane for unobstructed signals.
3. Threaded Nozzle Matching Probe Size: If the nozzle's inner diameter matches the probe's external thread, extend the probe >1cm beyond the nozzle to prevent retraction and ensure clear wave transmission.

2. Arched (Dome-Shaped) Tank Tops

1. Position the transmitter at 1/2 or 2/3 of the tank radius (away from the center) to avoid false echoes from the dome's focusing effect.
2. Use threaded nipples or flanges, adhering to nozzle proportions (e.g., 150mm length requires ≥100mm diameter; polish welds and chamfer at 45° for smoothness).
3. Ideal for avoiding lens-like reflections that could distort readings.

3. Open Tanks

1. Employ bracket mounting, ensuring the bracket's load-bearing capacity.
2. Keep the sensor at least 0.5m from the wall for 5m ranges or 1m for 10m ranges if walls are flat and free of obstructions.
3. Center installation is possible since open tanks lack focusing issues, but side mounting works well, too.

4. Drainage Wells and Ordinary Wells

1. For narrow, uneven wells, add a nozzle or full measuring sleeve (e.g., PVC/PE pipe ≥150mm inner diameter) to smooth the path—note that this increases the blind area by 50-100%.
2. In deep wells (>4m), consult the manufacturer for custom extensions.
3. Soak sleeves in the medium for accuracy, but keep them clean and seam-free.

Installing ultrasonic level sensors for measuring solids

1. Flange Mounting

1. Attach to the container's butt flange, ensuring the probe protrudes from the nozzle and is perpendicular to the solid surface.

2. Use a universal flange for easy rotation and alignment to prevent "wave drops" or jumps in data.

2. Threaded Pipe Installation

1. Expose the probe >2cm from the pipe bottom to maintain clear emission.
2. Suitable for nozzles where retraction could cause inaccuracies.

3. Frame-Type Installation

1. In open tanks or silos, align the probe axis with the container outlet or perpendicular to the medium surface.
2. For large open-air piles, use multiple transmitters on a lifting frame, each aligned with the pile's surface for comprehensive coverage.

Nozzle Extension Techniques

If site constraints prevent maintaining the blind area, extend the nozzle:

1. Keep the inner wall smooth and chamfered; avoid immersion in adhesive media to prevent buildup.
2. For non-adhesive media, immersion is fine for better isolation from container interferences.
3. Follow length-to-diameter ratios (e.g., 150mm length needs ≥100mm diameter; up to 400mm with ≥240mm).
4. Polish all joints and welds to eliminate burrs.

Once the installation is finished, the wiring and final setup can be done, then just take the following steps:

• Connect via (18-28)VDC power, with options for 4-20mA output, RS485 communication, or relays.
• Ground properly to prevent shocks, and use surge protectors for lightning-prone areas.
• After installation, calibrate for temperature compensation and test for echoes using the device's self-checking features.

How to maintain an ultrasonic level sensor?

Keeping the ultrasonic level transmitter in top shape is key to accurate readings in liquid and solid level measuring. Here’s a straightforward guide on how to maintain an ultrasonic level measurement based on common practices.

Regular simple check

Look it over monthly for scratches, rust, or gunk on the transducer. Wipe with a dry cloth if needed.

Sensor cleaning

Every few months, gently clean the emitting face with a soft brush or warm water to clear dirt, then dry it off.

Verify mounting and alignment

Make sure the transmitter is securely mounted and properly aligned to avoid signal interference or measurement errors.

Perform calibration checks

Periodically compare the transmitter’s readings with reference measurements and recalibrate if necessary to maintain accuracy.

Inspect for physical damage

Look for cracks, dents, or any physical damage on the unit that could affect its performance.

Check for moisture and condensation

Ensure the housing is sealed and dry to prevent moisture ingress, which can cause malfunctions.

Update firmware when needed

Install any manufacturer-recommended firmware updates to improve performance and fix known issues.