A gas meter with (a) a through-line and (b) a gas composition sensor for determining one of the parameters that characterises the composition of a gaseous fluid, with (i) a heat source for pulsed heating of the fluid to be measured, (ii) at least one thermometer (30, 32, 33) for time-dependent measurement of a temperature of the fluid and (iii) a control unit that is designed for the automatic - pulsed heating of the fluid to be measured by means of the heat source, - time-dependent measurement of the temperature ( T 30, T32, T33) of the fluid by means of the at least one thermometer (30, 32, 33) and - detection of the parameter using the at least one measured temperature ( T 30, T32, T33), (iv) wherein a distance (x 30) of at least one of the thermometers (30, 32) from the heat source is a maximum of 100 μm and (v) wherein the control unit of the gas composition sensor is configured to automatically - detect a through-flow of the gaseous fluid, - detect the parameter of the fluid that characterises the composition of a gaseous fluid in the form of an energy content parameter and - calculate the product of through-flow and energy-content parameter. (c) an inlet opening and (d) an outlet opening characterised by (e) a flow velocity reduction zone which - is in fluid connection to the inlet opening and the outlet opening and - is designed in such a way that an average flow velocity (v 35) in the flow velocity reduction zone is at most one tenth of an average flow velocity through the inlet opening (v 15), (f) wherein the gas composition sensor is arranged in the flow velocity reduction zone. (a) a through-line and (b) a gas composition sensor for determining one of the parameters that characterises the composition of a gaseous fluid, with (i) a heat source for pulsed heating of the fluid to be measured, (ii) at least one thermometer (30, 32, 33) for time-dependent measurement of a temperature of the fluid and (iii) a control unit that is designed for the automatic - pulsed heating of the fluid to be measured by means of the heat source, - time-dependent measurement of the temperature ( T 30, T32, T33) of the fluid by means of the at least one thermometer (30, 32, 33) and - detection of the parameter using the at least one measured temperature ( T 30, T32, T33), (iv) wherein a distance (x 30) of at least one of the thermometers (30, 32) from the heat source is a maximum of 100 μm and (v) wherein the control unit of the gas composition sensor is configured to automatically - detect a through-flow of the gaseous fluid, - detect the parameter of the fluid that characterises the composition of a gaseous fluid in the form of an energy content parameter and - calculate the product of through-flow and energy-content parameter. (i) a heat source for pulsed heating of the fluid to be measured, (ii) at least one thermometer (30, 32, 33) for time-dependent measurement of a temperature of the fluid and (iii) a control unit that is designed for the automatic - pulsed heating of the fluid to be measured by means of the heat source, - time-dependent measurement of the temperature ( T 30, T32, T33) of the fluid by means of the at least one thermometer (30, 32, 33) and - detection of the parameter using the at least one measured temperature ( T 30, T32, T33), - pulsed heating of the fluid to be measured by means of the heat source, - time-dependent measurement of the temperature ( T 30, T32, T33) of the fluid by means of the at least one thermometer (30, 32, 33) and - detection of the parameter using the at least one measured temperature ( T 30, T32, T33), (iv) wherein a distance (x 30) of at least one of the thermometers (30, 32) from the heat source is a maximum of 100 μm and (v) wherein the control unit of the gas composition sensor is configured to automatically - detect a through-flow of the gaseous fluid, - detect the parameter of the fluid that characterises the composition of a gaseous fluid in the form of an energy content parameter and - calculate the product of through-flow and energy-content parameter. - detect a through-flow of the gaseous fluid, - detect the parameter of the fluid that characterises the composition of a gaseous fluid in the form of an energy content parameter and - calculate the product of through-flow and energy-content parameter. (c) an inlet opening and (d) an outlet opening (e) a flow velocity reduction zone which - is in fluid connection to the inlet opening and the outlet opening and - is designed in such a way that an average flow velocity (v 35) in the flow velocity reduction zone is at most one tenth of an average flow velocity through the inlet opening (v 15), - is in fluid connection to the inlet opening and the outlet opening and - is designed in such a way that an average flow velocity (v 35) in the flow velocity reduction zone is at most one tenth of an average flow velocity through the inlet opening (v 15), (f) wherein the gas composition sensor is arranged in the flow velocity reduction zone.