Choosing the right level sensor: ultrasonic, radar or float?
Picking a level sensor comes down to your medium, accuracy needs, environment and budget. The three most common technologies — ultrasonic, radar and float — each win in different situations. This guide compares them so you can choose with confidence.
Quick comparison
| Ultrasonic | Radar | Float | |
|---|---|---|---|
| Contact with liquid | Non-contact | Non-contact | Contact |
| Affected by dielectric / foam | Foam: some | Low dielectric: some | No |
| Vapor / pressure / temperature | Best at ambient | Handles high P/T | Mechanical limits |
| Typical accuracy | mm-class | mm-class (higher) | Coarse / switch |
| Relative cost | Low–medium | High | Low |
| Best for | Most ambient tanks, water, open channels | High P/T, vapor, foam, harsh process | Simple high/low switching |
When ultrasonic is the right choice
Ultrasonic sensors measure level from above the tank without touching the liquid, so they avoid the corrosion, fouling and wear that affect floats. Readings are independent of color, transparency and dielectric constant, which makes them a strong default for water, wastewater, chemicals, oils and slurries in ambient-pressure tanks, ponds and open channels. They cost far less than radar while still delivering millimeter-class resolution — the best value for the majority of tank-level jobs.
Watch-outs: heavy foam, dense vapor or a vacuum/pressurized vessel can scatter or block ultrasound. In those conditions, choose an appropriate frequency and beam angle — or consider radar.
When radar is worth the premium
Radar (especially guided-wave) handles high pressure, high temperature, heavy vapor and foam better than ultrasonic, and offers the highest accuracy. The trade-off is cost and complexity. Reach for radar when the process is genuinely harsh or when ultrasonic's environmental limits apply.
When a float still makes sense
A float switch is simple, cheap and reliable for basic high/low level switching — pump control, overflow protection — where you don't need a continuous, precise reading. For continuous measurement or aggressive media, non-contact methods win.
How to decide in 4 questions
- Do you need continuous level or just high/low switching? Switching only → float. Continuous → ultrasonic or radar.
- Is the tank ambient pressure/temperature? Yes → ultrasonic is the value choice. High P/T or vapor → radar.
- Is the medium corrosive, dirty or sticky? Yes → go non-contact (ultrasonic/radar), not float.
- What's your budget per point? Tight → ultrasonic. Performance-critical harsh process → radar.
FAQ
Which level sensor is most accurate?
Radar is generally the most accurate, with ultrasonic close behind at millimeter class for ambient-pressure tanks. Floats give coarse or switch-only readings.
Is ultrasonic or radar cheaper?
Ultrasonic is typically much cheaper than radar while still offering millimeter-class resolution, which makes it the best value for most ambient tank applications.
Can ultrasonic sensors handle foam?
Light foam is usually fine; heavy foam can scatter the signal. Selecting the right frequency and beam angle helps — ask our engineers for foaming tanks.
What output do these sensors provide?
ATHENA ultrasonic level sensors support 4–20 mA, RS-485 and Modbus for direct connection to PLC, DCS or SCADA systems.
Choosing your sensor
For most ambient-pressure tanks and open-channel applications, an ultrasonic level sensor is the best balance of accuracy, reliability and cost. Tell us your tank height, medium, mounting and output, and our team will recommend a configuration.