Temperature Data Acquisition System for Showcase Refrigerator Based on ESP32 and Online Remote Display

In this paper, we discuss the utilization of ESP32 as an IoT device applied to a data acquisition system for monitoring temperature conditions within a showcase refrigerator. Within the showcase refrigerator, one section has its temperature conditions measured and recorded using a thermocouple sensor. The interface is facilitated by the MAX6675 module, with ESP32 serving as the processing unit. The temperature data is sent to Google Drive in the form of a Google Spreadsheet, enabling online access. Data visualization is conveniently accessible via a web app built using Google Apps. ESP32 connects to the internet via smartphone Wi-Fi. To validate the accuracy of temperature measurements, the results obtained from four thermocouple sensors were compared with readings from a precision glass thermometer. The second sensor exhibited the smallest error, whereas the other three sensors displayed increasing error rates when the temperature difference exceeded room temperature, with each thermocouple having an error of about 1.06, 0.58, 1.02, and 1.49 ℃. The reliability of the internet connection, facilitated by the smartphone, primarily hinges on the physical distance between ESP32 and the smartphone. It is less dependent on the smartphone's workload from other applications. At a distance of 12 m, the data loss percentage was recorded at 3%.