“The purpose of this project is to build a portable device, 3D printed, using an Arduino microprocessor and a mobile app, that can measure the speed of sound in gases and use this data to identify them.
The $ speed of sound in an ideal gas $ is related to two characteristics of the gaseous substance, its molecular mass in kg/mol and its adiabatic constant ( $ heat capacity ratio $ ), or its average values in case of being a mixture of gases.
It is for this reason that the measurement of the speed of sound can be used as a preliminary way to identify a pure gas or mixture of gaseous substances.
The measurement can be performed using an ultrasonic proximity sensor, to measure the round trip time ( t/2 ) of a sonic pulse in a tube of known length ( x ) ( $ echo method $ ), filled with the gas under study ( v = 2x/t ).
Since the speed of sound is also absolute temperature ( K ) dependent, it must be measured using a temperature sensor.”