Proximity sensor

Abstract

An immersion sensor for use with a cushion or mattress for determining the relative immersion of a person within the cushion or mattress comprising a sensor, a ground and a circuit for measuring capacitance. The sensor comprises a sheet of conductive material, and the ground comprises a second sheet of conductive material. The circuit is adapted to send short bursts of electrical current to the sensor and a capacitor. The circuit is further adapted to measure the length of time the burst of current takes to charge the capacitor. Based upon the measured time, the circuit calculates the proximity of the object based upon the time taken to charge the capacitor. A method that may be implemented with the immersion sensor is also disclosed.

Description

RELATED APPLICATIONS[0001]The present application is a continuation of application Ser. No. 11 / 412,859, filed Apr. 27, 2006, which claims priority to U.S. Provisional Application Ser. No. 60 / 725,901 filed Oct. 12, 2005, U.S. Provisional Application Ser. No. 60 / 725,006 filed Oct. 6, 2005, and also U.S. Provisional Application Ser. No. 60 / 675,315 filed Apr. 27, 2005. The contents of said applications are hereby incorporated by reference.FIELD OF THE INVENTION[0002]The invention relates to proximity sensors. More specifically, the invention relates to a sensor for detecting a relative distance of an object to the sensor by detecting changes in charge transfer.BACKGROUND OF THE INVENTION[0003]Proximity sensors for detecting an actual or relative distance between the sensor and an object are known in the art. For example, U.S. Pat. No. 6,621,278 to Arie Ariav discloses a method of measuring a distance by transmitting a cyclically-repeating wave. The wave is then received at a second loca...

AI Technical Summary

Benefits of technology

"The present invention is an immersion sensor that can measure a person's depth of immersion in a cushion or mattress. It consists of a conductive sheet and a reference conductive sheet, with a circuit that sends short bursts of electrical current to the sensor and measures the time it takes to charge a capacitor. This information is used to calculate the distance of the person's body from the sensor. The invention also includes a method for using the immersion sensor."

Problems solved by technology

However, this system has drawbacks, particularly in that the sensor is unduly complex both in electronic implementation and in sensor construction.

These detectors however cannot be used practically to detect a relative or actual distance, particularly in very short distances.

In certain settings, the amount of RF energy generated by these types of device is unacceptable due to interference.

Moreover, some people have concerns about constant exposure to RF energy.

However, often the people bound to the wheelchair do not have the ability to feel when they are properly immersed in the cushion, such as a paraplegic or quadriplegic person.

Similarly in a cushion not inflated with air, problems also exist when determining the proper cushion immersion.

However, presently, no acceptable means of detecting the immersion of a person in a cushion exists.

This type of measurement is dependant upon the materials of construction and structural conformation all creating significant limitations in the applicability of the measurement.

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