ULM series level transmitters are built on the operating principle of a chirp radar; this principle is better known as FMCW (frequency-modulated continuous wave) (hereinafter, we are using this abbreviation).The continuous principle (FMCW) is the most optimal for high-precision and weak-reflection level measurements, it ensures significantly higher level-measurement quality, a better level measuring accuracy, as low as possible effect of parasitic interference and interference caused by surface irregularities / waviness of a product to be measured, and improved measurement stability as compared to other (pulse) methods.