Some physical quantities are used for design of the various machine prototype, improvement research and determination of the operating circumstances. These physical quantities, which are widely known, are tension-compression forces, moment, distance, velocity, vibration, flow rate, pressure and revolution per minute values. Such parameters can be measured by appropriate measurement techniques. Nowadays, every kind of mechanical quantities can be converted electrical signal, transmitted, recorded or processed by electronic components. Physical properties of materials change under mechanical effects. The inductance, capacitance, resistance, reluctance and voltage of mineral materials vary if they expose to pressure. Thus, the pressure changes influencing on the material occur and mechanical changes transform into electrical signal in the electrical circuit. These converting methods are used a lot of areas in the agricultural machinery experiments; for example predicting the draught forces of tillage equipments, determination of loads on tractor structures or soil failure caused by subsoilers, and a general purpose tractor instrumentation.
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