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A new capacitance sensor system was developed with a microcontroller, commercial humidity and temperature sensors, a capacitance-to-digital converter, and a custom-built capacitance sensor. The performance of the system was evaluated by simulation and testing of the prototype. The impact of variations of ambient conditions on the system performance was analyzed, and a model for correcting the humidity and temperature influence was developed. Based on the experimental results obtained in an uncontrolled environment using a standard capacitor of 1 pF, the 24-h stability of the system was estimated to be within 30 parts in 106 . The high stability and sensitivity of the system allow its effective use in object-detection applications. Several sensors were constructed and evaluated while sensing various materials under different scenarios.