Ultrasonic Level Sensor Calculator
Ultrasonic level sensors rely on the speed of sound in air, which changes with temperature. Convert echo time to distance and level, and see the error if temperature compensation is missing.
- c = 331.3 × √(1 + T ÷ 273.15) = 351.89 m/s
- d = c × t ÷ 2 = 3.079 m
Speed of Sound in Air
d = c × t ÷ 2
T is air temperature in °C. The speed of sound rises by about 0.6 m/s (0.17 %) per °C.
Worked example
A 17.5 ms echo at 35 °C: c = 351.9 m/s and d = 3.079 m. A sensor fixed at 20 °C would read 3.003 m, about 76 mm short.
Frequently Asked Questions
Why does temperature affect ultrasonic level sensors?
The speed of sound in air rises with temperature, so the same echo time means a longer distance when warm.
What is the blanking distance?
A minimum distance close to the sensor where it cannot detect echoes while the transducer is still ringing.
Do vapours affect ultrasonic sensors?
Yes. Gases such as CO₂ or solvent vapour change the speed of sound and can absorb the signal; radar is better there.
Learn more on the blog
Ultrasonic level transmitter working
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
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