The sensitiveness of a balance is directly proportional to the lever arm and inversely proportional to the product of the distance of the axis of oscillation to the center of mass by the mass of the moving system. However, as the load increases, the central knife's edge and its support deform elastically, changing the line of contact to a surface with a larger frictional torque, decreasing the responsiveness of the balance to small increments of load. This is the main cause of loss of responsiveness as the load increases. It is possible to change the sensitiveness by means of a chain hung from an annular knife placed below the central knife, the other end of which can be raised or lowered. The elastic deformation of the central knife's edge and its support is avoided by turning the central knife's edge upward and making it touch lightly hard surfaces, supporting magnetically the weight of the moving system, thereby practically maintaining zero load responsiveness for all loads. By means of a servomechanism the beam is kept balanced and a suppressed zero record is made with a pen on a wide roll of paper which moves at uniform speed. It is thus possible to register the loss of mass of higher mammalians due to loss of water and metabolic processes.
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