Development of an ultrasonic helium concentration sensor

Nowadays, helium leak tests are largely used by many companies around the world to check the presence of leaks in their products and avoid problems arising. Helium is utilized because it has the smallest atom among the known elements and so it is perfect to detect even the smallest leaks. Beyond that, it is inert, and it is not dangerous as for example hydrogen. The most common type of sensor used to measure the helium concentration is the so called "thermal conductivity detector". It’s a device that computes the concentration using the difference of thermal conductivity between a carrier gas and a mixture of the carrier gas and column effluent gas. The sensor used by VAT, the company in which i wrote this thesis, is a thermal conductivity detector sensor that, right now, has several robustness problems: the aim of this project was to understand the weaknesses of the current solution and to solve them designing a novel helium sensor usable in VAT production. From the beginning, it was clear that modifying the current solution would have been too complex and not very productive. Then, it was decided to create something new from scratch, something more robust and able to meet the needs of the company: an ultrasonic helium sensor. An algorithm has been developed to calculate the helium concentration in real time and it has been tested in a real simulation environment Arduino based to verify its reliability. Lastly, having noticed that the algorithm worked well in principle, but the first prototype had some hardware limitations in gas applications, a second one was designed to exceed these limits and computing the helium concentration with the required accuracy.