Apparatus and method for level sensing in a container
US5895848A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 16, 1996 |
| Grant date | Apr 20, 1999 |
| Priority date | — |
| Expiry date | Jan 16, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/2967
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A liquid level sensing apparatus, and related method, that utilizes a tuning fork assembly to detect the presence of not only a liquid or air at a particular location within a container, but also a solid material at that location. The tuning fork assembly includes an excitation transducer and a receiving transducer mechanically coupled to a pair of paddles that are exposed within the container, and a phase-locked loop control system applies an excitation signal to the excitation transducer having a frequency that is regulated to track the tuning fork's resonant frequency. A comparator compares that resonant frequency with a prescribed threshold, to determine whether the tuning fork assembly is disposed in air or a liquid. A failure of the phase-locked loop control system to lock the frequency of the excitation signal at any particular frequency indicates that the tuning fork assembly is over-damped and likely contacted by a solid material. Since the apparatus normally excites the tuning fork assembly at its resonant frequency, this allows the apparatus to be operated at reduced power levels, leading to improved efficiency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.