Affiliation: | a Institute for Agricultural Engineering, Nussallee 5, University of Bonn, D-53115, Bonn, Germany b HKR Sensorsysteme GmbH, Gotzinger Strasse 56, D-81371, München, Germany c FOQ Piezotechnik GmbH, Riemenstr. 33, D-74906, Bad Rappenau, Germany |