2.1. Yield monitor
The system designed was based on: load cells as a
billet weighing instrument set up on the upper part of
the harvester side conveyor, just before the sugar cane
billets are dropped in an in-field trailer; inclinometer
sensor to measure the conveyor angle position in
relation to the ground; pre-filter techniques such as an
analogue Butterworth low-pass filter and digital filter to
eliminate the dominating frequencies; magnetic sensor
installed on the elevator axle, to determine the conveyor
speed; global positioning system (GPS) to indicate the
sugar cane harvester speed and location (longitude,
latitude, and altitude) in the field; data-logging system
PPC—A120 T (Advantech Co., Ltd., Milpitas, CA,
USA), with a NS Geode GX1 300MHz processor,
128Mb (SDRAM), 305mm touch screen monitor and a
PCI-1710HGL data acquisition interface 12-bit analogue/
digital (A/D) converter, with up to 100 kHz
sampling rate; and software based on C++ for
Windows designed to register the transducer readings,
and calculate the sugar cane yield.
The system designated Simprocana (Fig. 1) was
mounted on a Case 7700 sugar cane combine, and
evaluated during the 2004–2005 harvesting season, at
Sa˜o Joa˜o sugar mill, in Araras—the state of Sa˜o Paulo,
Brazil.