Probe assembly for a fluid condition monitor and method of making same

Abstract

A probe assembly for real-time monitoring of fluid state in a sensor using impedance spectroscopy, the probe assembly has two closely spaced tubular concentric electrodes. When the pitch is in the range of about 0.15 to 0.55 mm, the surface area of ​​the electrodes is about 8.1 to 10.8 cm2. In one embodiment, a concentric tubular outer Faraday shield is used to monitor fluid within a non-metallic container. This probe assembly is especially useful for monitoring hydraulic fluids, including automatic transmission fluids and mineral-based engine oils used in diesel and gasoline engines.

Description

technical field [0001] The present invention relates to sensors for providing real-time electrical indications of the instantaneous state of fluids in an operating system. In particular, the present invention relates to fluid state monitoring in fluids used for engine lubrication and hydraulic actuation in power transmission devices such as automatic transmissions of motor vehicles. Background technique [0002] It is known, as described in U.S. Patent 6,278,281 in the name of R.A. Bauer et al. and assigned to the assignee of the present invention, to employ impedance spectroscopy or impedance spectroscopy at different frequencies related to bulk fluid impedance and surface impedance of electrodes. Measurements to determine the state of operating fluids over time and service. The fluid condition monitor described above employs a pair of electrodes arranged with its interleaved unit in a generally planar array or as spaced apart parallel plates and arranged to be immersed in...

AI Technical Summary

Problems solved by technology

A disadvantage of the probe device of the aforementioned Bauer et al. '281 patent is that it is difficult to support and shield the device from mechanical interference, such as when the probe is to be immersed in elevated temperature motor vehicle transmission fluid or engine lubricant. In the case of mechanical disturbances due to vibration or fluid movement such as splashes or pressure disturbances

[0003] Furthermore, the electrode elements in the probes described above have proven to be difficult to place, especially where the electrodes are formed of thin material deposited on a substrate, making it difficult to provide the required surface area and spacing, not robust enough and expensive to manufacture

[0004] Moreover, problems have been encountered in providing a sufficiently high signal-to-noise ratio for the above-mentioned types of probes in fluid monitoring of the impedance measurement type.

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