Abstract: The concentration of optically active substances is determined by measuring the polarization of light passed through the substance using a light source, a polarizer and a modulator operated at a predetermined modulation frequency f.sub.F, as well as a measuring cell, an analyzer and a detector. The output signal from the detector 16 is alternately integrated during each half period of the modulation frequency to form voltage values U.sub.I+ and U.sub.I-. These voltage values are stored and the quotient Q of these stored voltage values is formed. Subsequently, an adjustable constant voltage is subtracted from the quotient. The measuring arrangement can have a miniature design for implantation. No mechanically moving parts and only a single detector are used. The measurement is accomplished by a simple, miniature linear ray path having high resolution.

Abstract: A contact arrangement comprising two cup-type contacts having hollow-cylindrical contact carriers arranged coaxially with each other and having slots inclined in the same sense to the longitudinal axis of the contact arrangement. The slots act as a coil for generating a magnetic field for minimizing arc currents. The condition ##EQU1## is met in a range of the outside diameter D of the contact carriers of from 60 to 150 mm, a predetermined height H.sub.T of the contact carriers, a number s of the slots and an azimuth B of the slots. With this design, a contact arrangement with an axial magnetic field of at least 3.5 uT/A is obtained.