Demand of CO2 gas sensors is expected to continue to increase in the foreseeable future, due to an increasing awareness of air pollution and fossil fuel emissions. A truly low cost and accurate NDIR sensor has the potential of greatly benefiting the environment by an increased human awareness due to CO2 measurements. In the objective to reach these goals, a CO2 sensor core on an ASIC needs to be investigated. In this study an ASIC prototype design is tested on an FPGA and evaluated towards logic resource requirements, power analysis and estimated cost impacts towards a full ASIC. The results show that a potential ASIC implementation would have a very small cost impact on a full system design if the use of a preexisting ASIC design is utilized. Using a manufacturing process of 180 nm, the total logic implementation would require between 0.54-0.76 mm2. The cost impact of such a logic area would be around $0.025 USD per chip. The power consumption of the logical part would also be very small when compared to the various analog components of a full system design.

Studien gick ut på att undersöka och ta fram relativa luftfuktighetsgivare som ger godkända mätvärden mellan [5%, 95%] relativ luftfuktighet med klimatkammare som referens. Med syftet att ersätta företagets givare i deras NDIR koldioxidsensor. Den skulle ersättas då deras nuvarande luftfuktighetsgivare gav felaktiga värden när klimatet gick mot antingen väldigt torrt eller fuktigt. Det är väsentligt att luftfuktighetsgivaren fungerar eftersom företaget använder värdena från givaren för att ge korrekta koldioxidmätningar i deras NDIR sensor. Detta är möjligt eftersom koldioxidhalter har visats sig påverkas av den relativa luftfuktigheten. Givarna införskaffades och monterades på PCB’s. Kod utvecklades för insamling av data genom I2C och SPI kommunikation. Givarna kördes sedan i en klimatkammare som svepte luftfuktigheten mellan [5%, 95%]. Värdena illustrerades i Matlab genom grafer. Givare 2 visade sig ge bäst värden på hela spannet jämfört med resterande givare. Den hade absolut minst avvikelse vid extrempunkterna, samt låg nära referensvärdet vid resterande luftfuktigheter i svepet [5%, 95%]. / The purpose of the study was to examine and bring forth a relative humidity sensor which gives approved values for the span between [5%, 95%] relative humidity with the climate chamber as the reference point. The goal was to replace the companies relative humdity sensor in their NDIR carbon dioxide sensor. It was to be replaced because their current sensor gave incorrect values when the climate was really humid or dry. It’s of value that the sensor gives correct values because the company uses relative humdity readings to correct their carbon dioxide reading in their NDIR sensor. The reason this works is because the carbon dioxide levels has been showed to correlate with the relative humidity. The sensors were studied and bought. They were mounted on top of PCB’s. Code was developed to gather data from I2C and SPI communication. The sensors was then put into an climate chamber and got swept between [5%,95%] relative humidity. The values were illustrated in Matlab through graphs. Sensor 2 proved to give the best values on the entire span [5%, 95%] relative humidity in comparison to the other sensors in the study. It had the least added error of all the sensors at dry/humid climates and was really close to the reference value at the other points of span [5%, 95%] relative humidity.

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