Development of a low-cost automated calorimeter for determining soil specific heat

• Published in: Computers and electronics in agriculture 2019-07, Vol.162, p.348-356
• Main Authors: Moreno, Rodrigo Oliveira, Armindo, Robson André, Moreno, Robson Luiz
• Format: Article
• Language: English
• Subjects: Automation; Clay loam; Clay soils; Low cost; Microcontrollers; Moisture content; Organic matter; Prototype; Prototypes; Reliability analysis; Soil thermal properties; Soil water; Specific heat; Texture
• ISSN: 0168-1699; 1872-7107
• DOI: 10.1016/j.compag.2019.04.015

•An automated calorimeter for measuring the soil specific heat is presented.•The prototype was developed with low cost material and the data acquisition system.•The prototype was tested with three soil textures.•Soil specific heat was determined ranging soil moisture and organic matter contents. This paper describes the development of an automated calorimeter for measuring the specific heat (c) of soil samples. An isoperibolic calorimeter prototype was developed with low cost material. The data acquisition system was based on an Arduino microcontroller paired with modular sensors. For testing the developed system, c determination was performed soils of three textures and varying soil water and organic matter contents. Results of soil specific heat for the soil water content range varied from 945 to 1876 J kg−1 K−1 for sandy clay loam texture, from 736 to 1154 J kg−1 K−1 for sandy texture and from 1099 to 2296 J kg−1 K−1 for sandy clay texture. For several organic matter contents in the sandy clay soil, c varied from 1105 to 1793 J kg−1 K−1. The reliability of the automated system was assessed by comparison to measurements of temperature, voltage and electrical current by a calibrated equipment, whereas measured c was also compared against results estimated with a known worldwide equation, confirming the reliability of the developed prototype and system of data acquisition.