Abstract: A liquid level sensor 10 includes spaced apart first and second temperature sensor 12, 14 and a heater 16 which is closer to the first temperature sensor 12 than the second temperature sensor 14. A temperature difference sensing circuit 18 provides an indication of the difference between the temperature sensed by the first and second sensor 12, 14 and more particularly the indication as to when this difference is above a threshold level. The sensors 12 and 14 and heater 16 are disposed within an elongated tube 22 made from a thermally conductive material with sensor 12 and heater 16 a distal end 26 of the tube and the temperature sensor 14 near a proximal end 28. The tube 22 is typically disposed horizontally within a sump. Temperature sensor 14 provides an indication of ambient temperature. Sensor 12 provides an indication of the temperature near the heater 16.

Abstract: A time delayed fluid level monitoring device (10) for monitoring the level of oil in a compressor sump (not shown) comprises a housing (12) which defines an internal cavity (18). Two orifices (20 and 22) are provided at end (16) of housing (12) to allow fluid communication between the interior of the compressor sump and the cavity (18). Orifice (20) is a restriction hole for restricting the flow of fluid between cavity (18) and the compressor sump so that there is a time delay between the equalization of fluid levels within the compressor sump and cavity (18). Orifice (22) is of a vent hole. A float (24) is pivotally supported within the cavity (18) as provided at one end (28) with a magnet (36) for switching a reed switch (26) extending through the housing (12).