Abstract: An oscillator is excited by a primary oscillator, and the excited oscillator is immersed in a fluid having two parameters, the first parameter of the fluid damping the excited oscillator via a first phase delay, and the second parameter damping the excited oscillator via a second phase delay. The oscillation of the excited and damped oscillator is detected as the oscillation signal. The oscillation signal is mixed with a phase-shifted signal generated from the excitation signal via a third phase delay which corresponds to either the first or the second phase delay. The mixed signal is averaged over time to determine the first or the second parameter according to the selection of the phase delay.

Abstract: Disclosed is a gas measuring device which comprises compensation of disturbances and offers high accuracy of measurement immediately after being activated. Said gas measuring device is provided with a gas sensor (1) for generating a measuring signal (S1) that depends on the gas concentration and can have a spurious component while a high-pass filter (13) having an adjustable limiting frequency mounted downstream of said gas sensor (1). The limiting frequency can be predefined according to the spurious component by means of a selection unit.

Abstract: A device for controlling a ventilation system in the interior of a motor vehicle includes a gas concentration determining arrangement to determine the exterior concentration of a gas in the exterior air surrounding the vehicle and to determine the interior concentration of the same gas in the air contained in the interior of the vehicle, and an air flow control arrangement, via which the proportion of circulating air and the proportion of fresh air from the surroundings of the vehicle in the air delivered to the interior by the ventilation system are controlled as a function of the determined interior concentration or the determined exterior concentration. The gas concentration determining arrangement is represented by a single gas sensor.