In recent years, the automotive industry has witnessed a significant shift towards integrating advanced technologies aimed at enhancing both safety and comfort within vehicles. Among these innovations, the integration of CO₂ sensors has emerged as a crucial element in ensuring optimal air quality, mitigating potential risks associated with CO₂ exposure, and detecting refrigerant leaks.

High levels of CO₂ can pose significant risks to human health. When exposed to elevated CO₂ levels, individuals may experience symptoms such as dizziness, headaches, and difficulty breathing. When using R744 as a refrigerant in vehicles, high concentrations of CO₂ can accumulate in the event of R744 leakage into the cabin when the vehicle is parked or when recirculation is used. Such leakage may stem from small holes, for instance, caused by rust formation.

To minimize the risks associated with high CO₂ levels, the SACD series continuously measures CO₂ inside vehicles. Mounted inside the cabin and based on the photoacoustic measurement principle, it ensures reliable and accurate measurements. Its compact design offers hidden in-cabin mounting and adjustable alarm levels allow for the setting of individual thresholds, enabling early warning signals.

Understanding CO₂ sensor technologies

Transmissive non-dispersive infrared (NDIR)
CO₂ molecules absorb specific wavelengths of infrared (IR) light. NDIR CO₂ sensors pass IR light through a measurement cell, using a detector to measure how much light is transmitted through it (i.e. not absorbed by CO₂ molecules). By comparison to a reference light intensity, CO₂concentration is derived. Two types of NDIR CO₂ sensors exist: single and dual channel. The reference measurement channel in dual channel NDIR enhances long-term stability.

Photoacoustic NDIR (PA)
PA uses a pulsed IR light source that emits wavelengths absorbed by CO₂. Absorption of light by CO₂ molecules leads to additional molecular vibration, increasing the pressure in the measurement cell. As the light source is pulsed, this pressure increase occurs periodically, creating an acoustic wave. The more CO₂ molecules present, the larger the amplitude of the acoustic wave. This is measured by a microphone to calculate CO₂ concentration.

Thermal conductivity (TC)
TC is based on the inherent thermal conductivity of all gases. With a thorough understanding of the gas composition in ambient environments, subtle changes in gas concentrations can be detected. The measurement principle is based on heating the air within a measurement cavity and sensing the heat transfer with a temperature sensor.

The incorporation of CO₂ sensors represents a significant advancement in automotive technology, offering a proactive approach to safeguarding passenger health, enhancing driver experience, and detecting refrigerant leakage. By leveraging innovative sensor technologies, automotive manufacturers can create safer, more comfortable, and environmentally sustainable vehicles for the future.

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