Abstract: An ultrasonic gas measuring device including a housing, end walls for the housing, the end walls having a gas inlet and a gas outlet provided therethrough, ultrasonic detecting means provided within the housing means, the ultrasonic means having a transmitter, operatively mounted on one end wall, and a receiver, operatively mounted on the other end wall, arranged at spaced locations within the housing, the housing incorporating gas processing means for dividing the gas flow at least at some instance during its flow through the housing, electronic circuitry functioning to detect and generate a signal in cooperation with the ultrasonic detecting means representative of the concentration of gas passing through the housing, the electronic means also generating a reference signal corresponding to the electronic signal delivered to the ultrasonic means, a phase shift provided within the electronic circuitiy and effecting a shift of one of said signals to furnish an aligned phased relationship between the two signal