Ultrasonic liquid level sensing system

Abstract

An ultrasonic probe having ultrasonic sensors (e.g., piezoelectric crystals) for measuring the level of liquid within a sealed container and having features that make the probe more reliable and enable more precise liquid level readings as the container nears an empty state. Embodiments include spacing the ultrasonic sensors more closely at the lower end of the probe, offsetting the sensors to enable tighter vertical spacing, matched pairs of sensors for redundancy, and a downward facing sensor located at the lower end of the probe to decrease the minimum liquid level that can be accurately measured by the probe. A sump may also be provided to further decrease the minimum liquid level that can be accurately measured by the probe.

Description

[0001] Cross References to Related Applications [0002] This application claims the benefit of U.S. Provisional Application No. 62 / 043,668, filed August 29, 2014. Co-pending US Patent Application No. 14 / 163,407, filed January 24, 2014, is incorporated by reference as if set forth in its entirety herein. Background technique [0003] Semiconductor manufacturing processes include the use of chemical reagents that must meet stringent purity requirements. These liquid chemicals are usually contained in sealed containers (eg, ampoules) to protect them from chemical contamination and to prevent leakage. Chemical reagents often require metal containers and container fittings that use metal-to-metal seals to avoid corrosion, contamination, or leakage under elevated pressure. When using chemicals stored in such containers, it must generally be possible to determine the amount of chemical remaining in the container without exposing the chemical to the environment or exposing the ope...

AI Technical Summary

Problems solved by technology

But these sensors are limited because they cannot accurately measure chemical agent levels near or below the lower end of the probe

This creates problems due to the precise nature of the semiconductor manufacturing process and environment, the costs associated with the chemicals, and the costs associated with disposing of residual chemicals when cleaning the container

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