The modular sensor network, consists of multiple sensorboxes, of which an example is displayed in Figure 1, which communicate wirelessly with each other. Each sensorbox contains multiple low-cost sensing components: Gas sensors that can detect NH₃, CO₂ and sensors that measure the barn climate, such as Temperature, Relative humidity and barometric pressure. The data can either be logged remotely in a cloud database owned by the manufacturing company, or it can be logged on a local computer.

Figure 1: Picture of a sensorbox

The readings of the low-cost sensors were compared to high-end analyzers, to assess the measurement quality. An example of a comparison between the CO₂ values of a sensorbox and an FTIR device are displayed in Figure 2 and a comparison between their respective NH₃ values in Figure 3. It is clear that the low-cost sensor is able to follow the concentration trends of the high-end FTIR analyzer. However, certainly for NH₃, the deviation of the sensorbox is still too large to trust the absolute values of the sensorbox readings.

Figure 2: Comparison of CO₂ measurements between FTIR and OTICE

Figure 3: Comparison of NH₃ measurements between FTIR and OTICE

The online dashboard consists of a set of open-source software tools widely available and documented. The graphical interface, on which the data can be visualized, is Grafana, a widely used dashboarding tool that offers a variety of options when it comes to display the data in a concise and clear manner. The data itself is stored in an open-source database InfluxDB. It is important to note that this sensor network needs to be calibrated, as the barn climate will influence the readings of the sensor components, which needs to be corrected. To incorporate the information of calibration as well as perform some cleaning before the data is stored in the database, a third software tool is used, called NodeRed, which is a graphical programming tool that makes programming more intuitive with graphical tools. NodeRed is also able to communicate with other sensor systems. This means that other sensor systems can be combined into OTICE, which makes it a flexible system for future developments. An example of a dashboard visualization in Grafana, which displays concentrations measured with a high-end picarro gas analyzer is shown in Figure 4. Each color denotes measurements in a different location in the barn, which is encoded in metadata when the measurements are collected.

Figure 4: Example dashboard of gas concentration measurements

An example dashboard of OTICE measurements is shown below. These sensors were installed as a plug-and-play system and collected data during the month of august 2024. Although the trends of the sensors reliably show trends in the barn air concentrations, a calibration will be necessary to improve the accuracy of these measurements in the future.

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