Key points
- Ultrasonic relies on the speed of sound, which changes with temperature and gas composition.
- Radar works in vapour, under pressure and in closed vessels.
- Narrow-beam 60 GHz radar avoids ladders, agitators and nozzle walls.
- Ultrasonic stays cost-effective for simple water applications.
The physics difference
Both time the echo from the surface. Ultrasonic uses sound, so the speed of sound in the air gap matters, and it changes by roughly 0.17% per °C and with vapour. Radar uses electromagnetic waves travelling at light speed, essentially independent of the gas space. Radar needs a reflective surface (dielectric constant, here ≥3).
Comparison
| Factor | 60 GHz radar (WSR201) | Ultrasonic (SUP-MP) |
|---|---|---|
| Accuracy | ±5 mm (≤10 m) | Typically ±0.2–0.5% of range, model-dependent |
| Beam | 6° | Wider cone |
| Vapour / steam | Unaffected | Affected |
| Pressure / vacuum | −0.1 to 0.3 MPa (this model) | Atmospheric only |
| Foam | Light foam OK | Absorbs sound |
| Range | 5/10/15 m | Up to 30 m |
| Cost per point | Higher | Lower |
Which to choose
- Closed process tanks, chemicals, heated liquids: radar.
- Open water, sumps, lift stations, flumes: ultrasonic.
- Heavy foam, or low-dielectric media under pressure: consider hydrostatic or DP level.
Related questions
Does radar need calibration?
Not against the medium. Configure tank height, blocking distance and range; the WSR201 is configured over Bluetooth.
Can ultrasonic work outdoors?
Yes, but wind, rain and sun-heated air gaps add error. Radar is more stable outdoors.
Sources and further reading
Product specifications quoted here are summarised from Supmea datasheets. Confirm the figures for your exact model before final design.