Successful application of ISE technology to real-time sensing of
hydroponic nutrients requires continuous determination of individual
nutrient concentrations with acceptable sensitivity and stability. In general, stability and repeatability of response are a
concern in the use of an array of multiple ISEs to measure ion concentrations
in a series of samples because accuracy of the measurement
may be limited by drift in electrode potential over time. The
use of a computer-based automatic measurement system would
improve accuracy and precision in the determination of nutrient
concentration because consistent control of sample preparation,
sensor calibration, and data collection can reduce variability
among multiple electrodes during replicate measurements (Dorneanu
et al., 2005; Kim et al., 2007, 2011). Ideally, an automated
sensing system for hydroponic nutrients would be able to periodically
calibrate and rinse the electrodes and continuously measure
nutrients in the hydroponic solution, while automatically introducing
solutions for calibration and rinsing as well as
measurement.