Precision Agriculture, 2, 119᎐130, 2000
ᮊ 2001 Kluwer Academic Publishers. Manufactured in The Netherlands.
Measuring Mass Flow by Bounce Plate for
Yield Mapping of Potatoes
DETLEF EHLERT email@example.com
Institute of Agricultural Engineering Bornim ATB , Di
ision Engineering for Crop Production,
Max-Eyth-Alee 100, D-14469 Potsdam, Germany
Abstract. There are reports about measuring mass flow in potato harvesters by X-ray with two wave
lengths sources, by load cells in conveyors and by optical surveying with image analysis. In mechanics, an
impulse is defined as the integral of force over time. If one succeeds in producing a constant velocity
difference in the mass flow of potatoes, then there exists a directly proportional correlation between the
integral force and the mass flow. A constant speed difference can be produced when the potatoes hit a
plate on which the potatoes bounce almost vertically in the discharge trajectory of a conveyor belt.
Under laboratory conditions, a rubber coated plate with a force measuring instrument was placed in
different positions in the discharge trajectory of a conveyor belt running at 3 different speeds. For
simulation of mass flow in steps of about 1 kg up to 40 kg, different masses of potatoes were placed on
the conveyor belt. For additional simulation of vibrations in a potato harvester, the measurement device
was moved horizontally, at five different frequencies and four amplitudes. The results showed a clear
linear relationship between mass flow and force. For many parameter combinations, the quality of fit
was more than 0.99 and, in some cases, standard error was less than 0.083 kg s
. The results indicated
that a bounce plate provides a basis for measurement in potato harvesters for yield mapping.
Keywords: yield mapping, potatoes, measurement, bounce plate
Surveying heterogeneity is an important part of precision agriculture because local
growing conditions for plants can vary considerably across a field. As a prerequisite
for site-specific cultivation and evaluation, this heterogeneity can be described with
parameters which can mainly be allotted to the soil conditions as cause, and to the
produced crop mass as the resulting effect. Yield maps are being generated by
combines, forage harvesters, balers, forage wagons, sugar beet harvesters and
potato harvesters. Research should be directed to finding the most suitable
methods for measuring mass or volume flows of crop materials for yield mapping.
As regards mapping of pototo yields, the basic measuring principles radiometric
measurement Baganz, 1991 , weighing cell in belt conveyors Campbell et al.,
1994 , image analysis Larsson, 1994; Persson, 1998 , bounce plate Ehlert, 1996,
1999 have been presented in the literature Fig. 1 .
Mass flows can be determined by measuring the attenuation of radiation
intensity Fig. 1ᎏtop left . The radiometric measurement can be carried out in the
flow of the product as a mixture of soil, stones and potatoes, and should allow
separate measurements of potatoes and accompanying mixtures. This was achieved