Patent Number: 6,192,751

Title: Non-invasive low frequency elastic wave fluid level sensing system forsludge laden environments

Abstract: A non-invasive elastic wave fluid level sensing system for use in sludge laden environments, including transmitting and receiving transducers mounted on an outer face of a wall of a container for a fluid and along a propagation path for an elastic wave transmitted through the wall of the container wherein the elastic wave has a frequency of less than 5 kHz, more preferably less than about 2 kHz, and most preferably less than 1 kHz. A signal processor determines a change in a characteristic of the elastic wave between when a fluid is present in the container in the region of the propagation path and when a fluid is not present in the container in the region of the propagation path. One embodiment utilizes multiple horizontally oriented transmitting and receiving transducer pairs to detect levels of the fluid in the container. Another uses a vertically oriented transmitting and receiving transducer pair and the characteristic of the elastic wave is dependent upon the proportion of the propagation path along which the fluid is present in the container, thereby indicating the level of the fluid in the container. The detector may include a cross correlation detector for determining the change in the characteristics of the elastic wave, the elastic wave preferably has a frequency of 1000 Hz or lower, and the elastic wave characteristic may be the propagation time of the elastic wave, the amplitude of the received elastic wave or the phase of the received elastic wave.

Inventors: Stein; Peter J. (Hollis, NH), Euerle; Steven Edmund (Nahsua, NH)

Assignee:

International Classification: G01N 29/02 (20060101); G01N 29/032 (20060101); G01N 29/44 (20060101); G01F 23/296 (20060101); G01N 29/50 (20060101); G01N 29/024 (20060101); G08B 021/00 ()

Expiration Date: 02/27/2013