Impact of Electrode Patterns Variation on the Response Characteristic of Leaf Wetness Sensors

Prediction of plant diseases is essential to reduce crop loss. Early disease prediction models have been investigated for this purpose, where data on leaf wetness duration (LWD) is one of the key components. Leaf wetness sensors (LWSs) are used to better understand how foliar wetness affects plant disease cycles and epidemic development. LWS can be fabricated on printed circuit boards (PCBs), where interdigitated electrode patterns are widely used. However, it is important to understand the efficacy of these patterns for in-situ measurements. For this purpose, in this work, we have fabricated three different patterns viz. circular, oval, and rectangular on the PCB and tested their efficacy during lab and field measurements. Lab measurements indicate that the circular patterned LWS offers a sensitivity of about 1600% over the dry-to-wet range, which is about 2 and 1.5 times more than oval and rectangular patterns, respectively. Besides this, circular patterned LWS offers the hysteresis of about 2%, whereas the oval and rectangular patterned LWS show about 3% and 7%, respectively. Field measurement results specify that circular patterned LWS and commercial LWS Phytos 31 indicate the same number of LWD events. However, oval and rectangular patterned LWS shows extra false events.