Ultrasonic gas sensor

A gas sensor, comprising:

• a main elongate gas chamber with a supply opening arranged on a first end of the main gas chamber and a discharge opening positioned opposite the supply opening and arranged on a second end of the main gas chamber, so as to permit gas to flow through the main gas chamber;
• a reference elongate gas chamber arranged in parallel fluid connection with the main elongate gas chamber;
• a magnetic field device configured to provide a magnetic field in the main gas chamber;
• an ultrasonic transmitter and receiver sensor arranged on either the first or second end of the main elongate gas chamber and being configured to direct an ultrasonic wave along a longitudinal axis of the main elongate gas chamber, an opposite end of the main elongate gas chamber being reflective for an ultrasonic wave, or an ultrasonic transmitter sensor arranged on a first end of the main elongate gas chamber and an ultrasonic receiver sensor arranged on a second end of the main elongate gas chamber;
• and
• a control unit configured to control the ultrasonic transmitter and receiver sensor and to determine a time of flight of the ultrasonic wave between transmitting and receiving the ultrasonic wave,
• wherein the reference elongate gas chamber is arranged outside the magnetic field generated by the magnetic field device.