Multi sensor node for long-term wireless measurement of density, pH value and temperature in silage for bio gas

A sensor node was designed, manufactured, tested and implemented to measure the density, the pH value and the temperature inside a stack of silage to increase the silage process efficiency for use in bio gas sites. The sensor node which comprises beside the multisensory system a wireless data communication unit, a battery, and an energy management system is described in this paper as well as the adjustment with a small model silo. A new sensor principle was developed for density measurements in inhomogeneous materials such as silage stacks.