An electromagnetically force-compensating force-measuring apparatus that includes a force dependent support coil and an integrating analogdigital converter that converts the coil current into a digital output signal. This invention also relates to the isocyanate mixtures obtained by this process, to their use for the preparation of blends with further isocyanates, and to the preparation of prepolymers containing isocyanate groups and of polyurethane plastics, preferably polyurethane foams from these isocyanate mixtures. The second logic circuit switches between supplying the detection signal to the inputoutput port and cutting off the detection signal to the inputoutput port. The electrodes are operative, in conjunction with the shaped geometry of the chamber where appropriate, to generate an electric field gradient in the titration chamber. Dispersed particles containing tungsten exist in both the lower layer and the upper layer. It uses the principle of sub-sampling to measure and amplify small clock skews and determine an estimate of clock skew by further manipulation if these sampled measurements.