METHOD FOR THE CLOSED-LOOP CONTROL OF A GAS MIXTURE USING A GAS SENSOR, A COMBUSTION-GAS SENSOR AND A GAS-MIXTURE SENSOR

The invention relates to a method for the closed-loop control of a gas mixture (9, 108) formed from a gas (2, 105) and a combustion gas (1, 103) in a combustion-gas-operated heating unit, wherein the gas mixture is produced by an amount of gas being provided via a first control element (4, 107) and an amount of combustion gas being provided via a second control element (3, 102) and said amounts being mixed, wherein a microthermal gas-mixture sensor (10, 107, 109), a microthermal combustion-gas sensor and a microthermal gas sensor are used in order to detect the material properties of the gas mixture, of the combustion gas and of the gas, and to use said material properties as controlled variables.