Electromagnetic force compensation scale with temperature compensation

A scale according to the principle of electromagnetic force compensation, comprising:

• a stationary permanent magnet system having an air gap;
• a position sensor for sensing position of the scale;
• circuit means connected with the position sensor, and including a control amplifier;
• at least one coil positioned in the air gap of the stationary permanent magnet system and acted upon, via the position sensor and the control amplifier, by a compensation direct current dependent on the load of the scale;
• said circuit means including an analog/digital converter and a measuring resistor, the same compensation direct current, flowing through the measuring resistor and at both ends of which a signal dependent on the load of the scale is tapped and fed to the analog/digital converter;
• and
• further electric circuits which permit an alternating current to flow, in addition to the compensation direct current, through the coil and the measuring resistor, and including a regulating device which modifies the amplitude of the additional alternating current in such a manner that the joulean heat generated in the coil and in the measuring resistor by the compensation direct current and by the additional alternating current is at least approximately load-independent.