[High linearity biologic impedancemeter (author's transl)].

A high linearity instrument for biological use which permits the measurement of impedance modulus and its variations in the range of 50 to 1,000 ohms is described. It has two outputs (Z and delta Z) which can be connected to an oscilloscope or to any conventional physiological recorder. The deviation from linearity is not greater than 0,06%, with a sensitivity of up to 100 mV/ohm, and an estimated average error better than 1% in absolute value with standard deviation better than 3% and an expected range smaller than +/- 10%. The instrument can stand changes of +/- 10% in the a.c. power supply without showing significant alterations in its behavior. Besides, it has good isolating characteristics in order to prevent undesirable leak currents which are potentially dangerous for the patient. The instrument was tested satisfactorily in human beings and in experimental dogs by recording respiratory movements and cardiac activity.