The dynamic characteristics of a rotameter type flowmeter has been investigated experimentally by making frequency response measurements using floats of various shapes and materials in two different liquids. The experimental results are compared with calculations based on a simplified theory which is derived. RBsume-La caract&istique dynamique d'un d&bitm&tre type rotametre a 6tC &udibe expMmentalement dans deux liquides diff&ents en faisant des mesures de dponse de frdquence, et en utilisant des flotteurs de formes et matikres varikes. Les r&ultats exp&imentaux sont compar& avec des calculs baa& sur une thborie simplill~e qui a &4 Btablie. Zusammenfassung-Die dynamische Charakteristik von Rotamessern wurde durch Frequenzgangmessungen experimentell untersucht in zwei verschiedenen Fliisslgkeiten unter Benutzung von Schwimmern verschiedener Gestalt und Mate&lien. Die experimentellen Ergebnisse werden mit Berechnungen verglichen, die auf einer eigens abgeleiteten vereinfachten Theorie beruhen. PREVIOUSLY published studies of rotameters have been confined almost entirely to considerations of their operation under conditions of constant liquid flow-rate and the relationship between the flow-rate and the height of the float in the tube. WHITWELL and PLUMB [l] derived a correlation between the flow-rate and the rotameter scale reading, using a modified form of Bernoulli's equation. This method involved the graphical determination of two functions, whereas the now generally accepted correlation, first proposed by SCHOENBORN and COLBURN [2], requiresthegraphical evaluation of only the rotameter coefficient K,, in the expression :