Strip chart recorder with a differential capacitor serving as position sensor in a position servo for the recording pen

Abstract

Abstract Strip chart recorders in which the curve is recorded by means of a rotatable pen (11) which traces the curve in a line of contact (14) being a generatrix of a supporting roller (15), suffer from a plotting error originating from the fact that the ordinate of the curve, which should be proportional to the angle of deflection v of the pen, is proportional to the tangent of said angle. This plotting error, that makes it impossible to carry out measurements on the curve, can be compensated for by incorporating in the position servo, which serves to overcome frictional losses in the recorder, a position sensor of a differential capacitor type (20, 22, 23) the differential capacitance of which, as a function of the angle of deflection v of the pen, is proportional to the tangent of v. According to one embodiment of the invention this is achieved by the rotor plate (20) and the stator plates (22, 23) of the differential capacitor each being bounded by a set of parallel lines (21, and 24, 25), and in that the differential capacitor, when being in its mid-position, displays mirror symmetry about a plane perpendicular to the plates and passing through a zero line (17).

Inventors

• 👤 Svend E. Fauerskov
• 👤 Svend O. Sjostrom

Bibliographic Details