The thermal mass flow controller WF 6500 operates on the constant overtemperature principle and has an integrated control valve. Due to its simple, robust construction, but also due to its precision, the WF 6500 is suitable for a wide range of applications, from analysis to rough industrial operation. The integrated control valve has a modular design, the control circuit is located on the circuit board. The reference value can be set by an external control unit. The small dimensions, as well as the possibilities of an integrated LCD display, allow an easy installation.