Inline quality monitoring of diesel exhaust fluid (AdBlue) by using the 3<i>ω</i> method

• Main Authors: R. E. Bernhardsgrütter, C. J. Hepp, M. Jägle, H.-F. Pernau, K. Schmitt, J. Wöllenstein
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-01-01
• Series: Journal of Sensors and Sensor Systems
• Online Access: https://jsss.copernicus.org/articles/10/5/2021/jsss-10-5-2021.pdf

<p>Because diesel combustion processes produce harmful detrimental nitrous oxides, the selective catalytic reduction, an after-treatment method using diesel exhaust fluid (AdBlue) to reduce these emissions, is an important part in the cycle of the combustion process. Therefore, it is crucial to continuously monitor the quality of the diesel exhaust fluid to secure the ideal selective catalytic reduction. This article presents a platinum thin-film sensor using the 3<span class="inline-formula"><i>ω</i></span> method which is able to characterize the diesel exhaust fluid. By means of the 3<span class="inline-formula"><i>ω</i></span> method, information about the concentration of urea in water can be extracted. In this investigation, a digital lock-in amplification technique is used to execute the measurements. The results show that this sensor can determine the urea content within 1 % by weight. Moreover, besides the analysis of the 3<span class="inline-formula"><i>ω</i></span> signal, the 1<span class="inline-formula"><i>ω</i></span> signal is analyzed in depth to receive additional information about the temperature. Because the same structure can measure multiple parameters, such as concentration, temperature, and flow, the sensor might be a good alternative to the state-of-the-art diesel exhaust fluid sensor.</p>