Level Measurement · Glossary

What is an Ultrasonic Level Transmitter?

non contact sound pulsesLevel Measurement

An ultrasonic level transmitter measures level from the time sound pulses take to travel to the liquid surface and back.

Ultrasonic Level Transmitter Explained

A transducer at the top sends sound pulses and listens for the echo. The time, with the speed of sound in air, gives the distance to the surface.

Speed of sound changes with temperature, so a built in temperature sensor corrects it. Ultrasonic is cheap and suits water, sumps and open channels, but struggles with vapour, foam, pressure and dust.

Ultrasonic Level Transmitter Formula

d = c × t ÷ 2 with c ≈ 331.3 + 0.606 × T

c	speed of sound in air (m/s)
T	air temperature (°C)
t	round trip time (s)

Example: At 20 °C, c ≈ 343.4 m/s; a 10 ms echo gives d ≈ 1.72 m.

Calculators for Ultrasonic Level Transmitter

CalculatorUltrasonic Level CalculatorFree online calculator with formula and worked example.CalculatorWeir Flow CalculatorFree online calculator with formula and worked example.CalculatorTank Ullage CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadLevel Transmitter Datasheet Template in ExcelFree download in Excel and PDF.

Frequently Asked Questions

What is an Ultrasonic Level Transmitter?

An ultrasonic level transmitter measures level from the time sound pulses take to travel to the liquid surface and back.

Why does an ultrasonic level read wrong in a closed tank with vapour?

Vapour changes the speed of sound; the meter compensates only for air temperature.

Ultrasonic or radar?

Ultrasonic for simple water service at low cost; radar where vapour, temperature, pressure or foam would upset sound.

Learn more on the blog

Ultrasonic level transmitter working

A practical guide on instrumentationblog.in with more detail on ultrasonic level transmitter and how it is applied on real plants.

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