Utilization of Integrated AM Receiver Circuit in Contactless Conductivity Detector for Detections in Solution

Abstract

The integrated circuit TDA 1072A (Philips) was tested in signal processing in a contactless conductivity detector. The detection cell (consisting of two tubular electrodes placed on the outer wall of a PTFE tube) was connected between the sine-wave generator output and antenna input of the circuit. The analytical signal, a DC voltage, was taken from the output of a field intensity indicator. For the sine-wave input of the voltage frequency 1330 kHz and amplitude 0.25 V(pp), a nonlinear dependence of the signal on the solution conductivity was obtained in the range from ca. 25 to 700 μS cm^-1, corresponding to the KCl concentration from 2.10^-4 to 5?10^-3 mol l^-1. The relative standard deviation of the conductivity values was ca. 1 %. The detector was used for evaluation of drinking water.