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An automated nutrient replenishment system has been developed in order to provide a constant electrical conductivity (EC) value for the nutrient solution over the period of plant growth. A single nutrient film technique (NFT) system developed by the Tuskegee University NASA Center was equipped with the EC control system for growth trials with sweetpotatoes. The system is completely controlled and monitored by a PC through the use of LabView instrumentation and data acquisition software. A submersible EC probe driven by an EC controller measures the EC of the nutrient solution reservoir. EC values are passed from the controller to the PC through analog outputs. If the EC is outside a given range, the PC sends a signal to one of two solenoid valves that allow concentrated stock solution or deionized water to enter the reservoir to either raise or lower the EC respectively. For this application the set point is 1200μS cm-1, with a dead band from 1180 to 1220μS cm-1.

An automated Data Acquisition System (DAS) for managing and controlling an aerobic biodegradation process of solid biomass has been developed. The system employs a personal computer equipped with a data acquisition card and a visual basic software (LabVIEW). The DAS was integrated with the physical / chemical hardware (a bioreactor with its auxiliary equipment) through the necessary sensing devices. These sensing devices include in-line electrical-conductivity (EC), pH, and temperature probes. A flow sensor was inserted in the circulating sampling line to ensure that the in-line manifold does not contain air bubbles or clogged with fine particles. A gas analyzer was used to sample off-gases from the bioreactor to measure and record the change in the CO2 and O2 levels. The data acquisition system is capable of controlling the pH level inside the bioreactor by activating acid or base metering pumps.