Thermal liquid level detector
US4564834A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 11, 1983 |
| Grant date | Jan 14, 1986 |
| Priority date | — |
| Expiry date | Oct 11, 2003 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T137/7306
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A pair of PTC elements, preferably of the barium titanate variety, are mounted in a container to sense liquid level, for example oil level in an engine crankcase. The elements have the same resistance, mass and switching point but different thermal loss coefficients which have one value in air and another in liquid. In one embodiment, the elements are both positioned at the set liquid level and are electrically energized at the same moment. When the elements are in liquid, one of them will heat to the switch point before the other and change to a much higher resistance. When the elements are in air, the other element reaches the switch point first. When the elements are connected in series across a power source, the switching causes the circuit to latch in that state even though the liquid level condition changes. The junction of the elements provides a convenient signal output indicating liquid level. In a second embodiment, one PTC element is at the set liquid level and the other is in air above that level. Again, the liquid level determines which PTC element wins the race when electrically energized.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.