There are various sizes of pneumotachometers with various ranges of flow rate, designed for use in a wide range of animals. The differential pressure is 6.25 mmH2O at the normal flow rate of all models. The tube has a 4-Volt heating element which prevents condensation of the moisture in the expired air (4-Volt power supply for heating Fleisch Tube). Respiratory flow during inspiration and expiration is measured in ml/sec by a pneumotachometer (Fleisch Tube) in form of a differential pressure. For converting this pressure into an electrical signal the pneumotachometer has to be connected to a differential pressure transducer. Rigid and short plastic tubing is required for connection to the differential pressure transducer.