A Soil Yeast Count Monitor for Plant Growing Applications

A soil yeast count monitor that includes a soil yeast sensor and converter was developed for plant growing applications. The monitor can linearly transform soil yeast count into a frequency output. Moreover, the monitor’s adjustable sensitivity control circuits can increase sensitivity when low-nutrient soil is used. During measurements, the input voltage of the proposed converter was 0 to 2.2 V, and the sensitivity was controllably adjusted by 2.217, 2.952, 3.651, 4.388, and 5.118 MHz/V. The range of soil yeast count was 0 to
$7\times10$
⁸
colony forming units (CFU), and the adjustable sensitivities were 0.654, 0.871, 1.091, 1.311, and 1.529 MHz/10
⁸
CFU. The maximum linear error of the complete system was −0.66%, and the chip size was
$1.49\times1.49$
mm
²
. The system was experimentally tested on two types of soil: fluvisol and paddy soil. Through measurements and experiments, the soil yeast count monitor was proven functionally.