DEVICE FOR DETERMINING HUMUS CONTENT IN SOIL
The authors report on a newly developed device for express control of humus content in soils, which makes it possible to carry out their analysis at minimum costs. The electrical resistance of soils has been studied as an objective and easily determined diagnostic indicator of agroecological assessment of soil properties. The developed instrument contains the nodes for amplification and conversion of the signal coming from the measuring electrodes, and the nodes forming the probing signal of a constant or alternating current of a given magnitude. The path of conversion and amplification of the signal coming from the measuring electrodes includes an input filter, an input amplifier, a low-frequency generator, an amplitude detector, and an analog-to-digital converter with a display. The principle of measuring the electrical resistance of soil is based on the use of a multi-electrode sensor. At the same time, a probing voltage of direct or alternating current (0.1, 1.0 and 10 mA and frequency 1, 10 or 100 kHz) is applied to the electrodes, and a signal proportional to the electric resistance of soil (between the electrodes) is removed from the measuring electrodes. A significant advantage of this device is the reduction of the measurement error due to the use of an alternating current as a probing signal, the specific electrical resistance being calculated per unit area [Ohm*sq.m], instead of unit length.