An annular absorbent filter element of a sensor probe is exposed to fluid while held by one end of a coil spring in contact with magnetic and non-magnetic discs non-conductively spaced from a third non-magnetic disc to supply a contamination signal to a two-stage detection circuit through which internal deterioration conditions of machinery are monitored. Electrically conductive and magnetic flux paths are established through the filter element and a flux gap to magnetically attract contaminants and establish parallel connected, variable resistances through which said contamination signal is derived. The signal output of the sensor probe thereby provides an early warning alert to prevent machinery damage.
A system for detecting the presence of moisture in the refrigerant of a refrigeration system and providing a signal to indicate the presence of moisture and shutdown the refrigeration system thereby avoiding damage and possible failure of the refrigeration equipment. The device is in the form of a probe or probes inserted into a flow path or flow paths of the refrigerant and an assembly for providing an audio-visual signal or alarm and shutting down the machinery prior to it becoming damaged by the moisture or water in the refrigerant.