The invention is an apparatus and method for measuring the flow rate of a liquid through a conduit. The apparatus is based on a flow rate meter which is adapted to accurately measure the volumetric flow rate of a liquid using a simple, cost and energy effective, and accurate method using only one temperature sensor. The method is based on applying a pulse of thermal energy to the flowing liquid and measuring the temperature increase as a function of time and energy input. By comparing these measurements to a calibration table made by performing similar measurements for known flow rates, the rate of flow can be determined. One application, which will be described to illustrate the features of the method and apparatus of the invention, is measurement of the flow rate of urine excreted by a catheterized patient.
