A Low-cost Automatic System for Long-term Observations of Soil Temperature

The description of the physical parameters characterizing heat transport in the soil medium, especially on a regional scale, requires long-term and high frequency observations of temperature changes in soil profiles. This paper presents a project for a multi-channel, modular and universal data logger for temperature distribution data collecting in the soil profile, based on open electronic components, such as Arduino microcontroller systems and DS18B20 thermometers. The data logger tests were carried out in two profiles. The seven-month tests did not show any errors in the functioning of the measurement set. The presented device requires an average current of 320 µA, which allows for its stable operation on one battery set for about 300 days in temperate climate conditions. The DS18B20 thermometers allow for accurate and stable temperature measurement (the mean absolute error after laboratory calibration was 0.02°C). The cost of a single measurement-registration device was approximately 76 EUR, representing a competitive price in comparison with commercial data loggers. This allows, with relatively low expenditure, the creation of extensive observation networks for the analysis of the heat flow process in high temporal and spatial resolution.