Gas burner having a servo gas system with a hydraulic Wheatstone-bridge controlling an electric fuel supply valve, and method of operating such a gas burner

Servo gas system (11) realised as a modified hydraulic Wheatstone bridge for a gas burner (10), namely for controlling a pressure regulation valve (20) positioned in a gas duct (18) of the gas burner, thereby controlling a pressure difference between a pressure (P1) in a burner chamber (12) of the gas burner and the gas pressure (P6) within the gas duct (18). The hydraulic Wheatstone bridge embodiment comprises a static servo gas flow branch (28) and a dynamic servo gas flow branch (29) being connected in parallel, a flow sensing element (30) being connected between the static servo gas flow branch (28) and the dynamic servo gas flow branch (29) and providing a signal used to control the pressure regulation valve (20) by an electric actuator (41). The static servo gas flow branch (29) comprises a first (32) and a second flow restricting device (33) in serial connection. The dynamic gas flow branch (29) comprises a pressure regulator (37) and downstream of the pressure regulator (37) a third flow restricting device (38) in serial connection. The flow sensing element (30) is connected to the connection between the two flow restricting devices (32, 33) of the static servo gas flow branch (28) and to the connection between the pressure regulator (37) and the third flow restricting device (38) of the dynamic servo gas flow branch (29). The pressure regulator (37) is further connected to a reference pressure, preferably the combustion chamber pressure (P1).