A new instrument for the measurement of liquid level has been developed, which makes use of the fact that an electric pulse advancing on a transmission line is reflected from any point on the line where the line impedance changes abruptly. Such a change of impedance is obtained at a sudden change of the dielectric constant in the transmission line, i.e., if a fluid is partially introduced in the line. The instrument is further based on the sing‐around principle, which gives directly a digital output signal of high accuracy and linearity, in the order of ±0.02%. The instrument can be used for all liquids having a dielectric constant greater than 1.1 or sufficient electrical conductivity.