V. Prošek

The mathematical model of experimental sensor for material distribution detecting on the conveyor

Much research has already been devoted to various electrical capacitance techniques for determining the flow of material or to define the material distribution. Simple electrical capacitive throughput sensors, but also very complex electrical capacitance tomograph sensors were tested. An interesting compromise may be segmented capacitance sensor (SCS). In this paper, a mathematical model of SCS is verified. Two mathematical models are compared. The first model simplifies the problem by the use of the electrostatic field. Using the second model a variable electric field at low frequencies is described. It was found that, for an easier description of the SCS electric field, this field can be considered as the electrostatic field. Measurements carried out, for the most part supported the correctness of the mathematical model. Some deviations were probably caused by transferring the problem to 2D.

Segmented Capacitance Sensor with Partially Released Inactive Segments

Abstract Material throughput measurement is important for many applications, for example yield maps creation or control of mass flow in stationary lines. Quite perspective can be the capacitive throughput method. Segmented capacitance sensor (SCS) is discussed in this paper. SCS is a compromise between simple capacitive throughput sensors and electrical capacitance tomography sensors. The SCS variant with partially released inactive segments is presented. The mathematical model of SCS was created and verified by measurements. A good correspondence between measured and computed values was found and it can be stated that the proposed mathematical model was verified. During measurement the voltage values on the inactive segments were monitored as well. On the basis of the measurement there was found that these values are significantly influenced by material distribution.

Parallel Plate Mass Flow Sensor for Forage Crops and Sugar Beet

Measurements described in this paper were realized in order to find out whether there is some relationship between mass flow of plant material passing through a parallel plate capacitive sensor and its output signal. This possibility of mass flow determination could be useful for the aim of forage crops or sugar beet yield maps creation. A parallel plate capacitive throughput sensor was designed for that purpose. The capacitive sensor and the whole oscillating circuit were driven at 27 MHz frequency. The laboratory set-up consisted of a conveyer belt, carrying a measured quantity of material into sensor, equipped with an electronic measurement apparatus. Material passed through the sensor between its plates. Laboratory tests were carried out with forage crops and with sugar beet. Resulting coefficients of determination ranged from R2=0.95 to 0.97 for forage crops and around R2=0.98 for sugar beet. It was possible to conclude from our measurement that forage and sugar beet mass flow determination by means of the parallel plate capacitive sensor is a promising way. The results showed a strong linear relationship between the feed rates of plant material passing through the sensor and tested measuring capacitive sensor circuit output signal.

Capacitance Sensor for Forage Mass Determination

Non-contacting methods for material properties determination and crop yield determination are the best solution especially for rough conditions in agriculture, however, it requires reliable and durable sensors as a source of primary data. The capacitance sensor based technique can be used for forage material mass determination in order to utilize obtained data for yield maps creation.