Liquid level sensor with improved temperature range

摘要

An ultrasonic liquid-height detector employs conductive rods extending from a housing, and corresponding transducers, into a liquid, where elastic seals surround the rods at their exit point from the housing. Acoustic crosstalk between the rods through the seals and the housing (rather than through the liquid) is minimized by displacing the seals from each other as measured through the housing to increase a path length through the housing so that the crosstalk energy is delayed with respect to the direct energy indicating liquid height. A sampling window is positioned to sample transmitted sound across the rods at a time before the arrival of the crosstalk energy.

主权项

1. A liquid level sensor comprising:
a housing holding an ultrasonic transmitting transducer and an ultrasonic receiving transducer; first and second ultrasonic conducting rods each communicating respectively with one of the transmitting transducer and receiving transducer and extending out of apertures in the housing to be received within a liquid to be measured, the ultrasonic conducting rods being separated across a gap receiving liquid therebetween; seals between the first and second ultrasonic conducting rods and corresponding apertures in the housing; wherein the seals are positioned to provide: (a) a first acoustic delay along a shortest acoustic path from the transmitting transducer through the first ultrasonic conductive rod through a first seal through the housing to the second seal through the second ultrasonic conducting rod to the receiving transducer that is longer than: (b) a second acoustic delay along a shortest acoustic path from the transmitting transducer through the first ultrasonic conductive rod through the liquid to the second ultrasonic conducting rod to the receiving transducer for at least one liquid level with respect to the ultrasonic conductive rods; wherein the first and second ultrasonic conducting rods extend through the apertures in an extension direction away from the transmitting transducer and receiving transducer to provide a gap between exposed portions of the first and second ultrasonic conducting rods displaced from the seals in the extension direction so that the seals may be removed from liquid between the exposed portions.