APPARATUS AND METHOD FOR TAKING THE DERIVATIVE OF A SLOWLY VARYING ELECTRICAL SIGNAL

摘要

An electrical circuit for operating upon a slowly varying input signal (on the order of one volt per minute) to provide as output signal representative of the input signal derivative. The circuitry employs at least two feedback loops, one of which is constructed similar to an integrator amplifier. One particularly useful electro-medical application of this apparatus and method lies in the measurement of osmotic fragility of red blood cells, where percentage hemolysis of the blood slowly varies as a function of tonicity of suspension of the medium in which the blood sample is suspended. In this measurement the exact point of maximum slope is important and is provided by the present invention.