A system comprising: a flow sensor configured to be disposed in a conduit in fluid connection with a flow of a gas through the conduit, the flow sensor including a heater and at least one temperature sensing element , the flow sensor configured to generate an electrical output based on the flow of the gas through the conduit ; and a controller including one or more processors operatively connected to the flow sensor and configured to control operation of the heater at multiple measurement intervals, the controller operable in a pre-measurement mode and multiple measurement modes, the controller in the pre-measurement mode operating the heater at a pre-measurement setting, the controller in the measurement modes operating the heater at corresponding measurement settings that have at least one of increased power levels or longer operating durations relative to the pre-measurement setting of the heater, the controller in the measurement modes configured to determine a flow rate of the gas based on at least one of an amplitude characteristic or a temporal characteristic of the electrical output of the flow sensor ; characterised in that during each measurement interval, the controller operates in the pre-measurement mode and is configured to determine whether or not to operate in any of the measurement modes during a current measurement interval based on a dynamic response in the electrical output of the flow sensor to the heater operating at the pre-measurement setting, wherein said dynamic response represents the electrical output of the flow sensor as the heater warms up and cools down. a flow sensor configured to be disposed in a conduit in fluid connection with a flow of a gas through the conduit, the flow sensor including a heater and at least one temperature sensing element , the flow sensor configured to generate an electrical output based on the flow of the gas through the conduit ; and a controller including one or more processors operatively connected to the flow sensor and configured to control operation of the heater at multiple measurement intervals, the controller operable in a pre-measurement mode and multiple measurement modes, the controller in the pre-measurement mode operating the heater at a pre-measurement setting, the controller in the measurement modes operating the heater at corresponding measurement settings that have at least one of increased power levels or longer operating durations relative to the pre-measurement setting of the heater, the controller in the measurement modes configured to determine a flow rate of the gas based on at least one of an amplitude characteristic or a temporal characteristic of the electrical output of the flow sensor ; characterised in that during each measurement interval, the controller operates in the pre-measurement mode and is configured to determine whether or not to operate in any of the measurement modes during a current measurement interval based on a dynamic response in the electrical output of the flow sensor to the heater operating at the pre-measurement setting, wherein said dynamic response represents the electrical output of the flow sensor as the heater warms up and cools down. <EOS>