Weighing cell based on the principle of electromagnetic force compensation with optoelectronic position sensor

摘要

A weighing cell (1) based on the principle of electromagnetic force compensation includes a stationary base part (2), a load receiver (3) constrained to the base part (2) in guided movement and serving to receive the weight force of a weighing load (4), and further includes a permanent magnet system (5) mounted on the base part (2) and having an air gap (6). Suspended in the air gap is a coil (8) which is connected to the load receiver (3) through a force-transmitting mechanism (9) and which carries an electrical compensation (7) current when the weighing cell (1) is in operation. Further included is an optoelectronic position sensor (12, 13) whose sensor signal (14) corresponds to the deflection of the coil (8) from a zero position which occurs as a result of placing a load (4) on the load receiver (3). A closed-loop controller (15) regulates the compensation current (7) in response to the sensor signal (14) in such a way that the coil (8) and the load receiver (3) that is connected to it are returned to their zero position by the electromagnetic force that is acting between the coil (8) and the permanent magnet (5). The optoelectronic position sensor includes a light emitter (12) and a light receiver (13) which are mounted on the base part (2) with an interstitial space between them, as well as a shutter vane (10) traversing said interstitial space and participating in the movement of the coil (8). The light emitter (12) is mounted on a first carrier element (16, 116, 316), centered on the connecting line (VI) between two first fastening locations of the first carrier element (16, 116, 316), the latter being rigidly attached to the base part (2, M830-E EP Translation - 25 - 202) through the first fastening locations; and/or the light receiver (13) is mounted on a second carrier element (17, 117, 317), centered on the connecting line (V2) between two second fastening locations of the second carrier element (17, 117, 317), the latter being rigidly attached to the base part (2, 202) through the second fastening locations.