A tool has been proposed that allows rapid analysis to measure relative humidity during experimental research on the decomposition of municipal solid wastes for the development of highly efficient garbage trucks as the main link in the structure of machines for the collection and primary processing of municipal solid wastes. The structural scheme of the device for measuring relative humidity is given. A block diagram of the microcontroller control program algorithm for measuring relative humidity has been developed. The main characteristics of the proposed device are given. Calibration and experimental tests to measure the relative humidity of municipal solid wastes were conducted. As a result of the experimental studies presented in the work, the reliability of the measured parameter is confirmed.