Importance

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Abstract

A contamination monitoring system is disclosed wherein a low frequency alternating current signal is applied to a remotely mounted probe in the liquid being monitored for contamination. A fixed resistor located at the probe is electrically in parallel with the resistance of the liquid being monitored. The resistor is isolated from the liquid and allows a signal to be transmitted through an interconnecting cable even though the liquid resistance is very high. A signal is returned to signal processing electronics via the interconnecting cable to a high input impedance amplifier which drives an isolation transformer. The isolated electrical signal induced on the secondary winding of the isolation transformer drives a two stage amplifier circuit the output of which is representative of the amplitude of the isolated electrical signal which in turn is representative of the resistance of a path between the alternating current signal generating means and the high input impedance amplifier that drives the isolation transformer. The representative resistance is applied to three comparator circuits that indicate and alarm the three conditions; (a) an increase in conductivity in a normally nonconductive liquid, (b) an abnormally high conductive condition indicative of a short circuit and (c) unusual increases in nonconductive measurments which would indicate open circuit conditions in the cable.

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First Claim