HIGH LINEARITY BIOLOGIC IMPEDANCEMETER

Abstract

A high linearity instrument for biological use which permits the measurement of impedance modulus and its variations in the range of 50-1000 .OMEGA. is described. It has 2 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/.OMEGA., and an estimated average error better than 1% in absolute value with SD better than 3% and an expected range smaller than .+-. 10%. The instrument can stand changes of .+-. 10% in the AC power supply without showing significant alterations in its behavior. It has good isolating characteristics which 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.