News Column

Patent Application Titled "Open Potentiometer Detection System" Published Online

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventor Jefferies, Kevin (Raleigh, NC), filed on December 31, 2012, was made available online on July 10, 2014.

The assignee for this patent application is Schneider Electric Usa, Inc.

Reporters obtained the following quote from the background information supplied by the inventors: "Potentiometer applications include a wide variety of electronic devices and uses within the devices. Potentiometers are commonly used to provide input from sensors and controls, by achieving a defined relationship between a mechanical position and a variable resistance. An electronic measurement system monitors the dependent resistance characteristic of the potentiometer to determine the mechanical position, and subsequently an output voltage related to the position of the device is determined. One example application of a potentiometer is an adjustment dial for a user interface to an electronic motor overload relay.

"These electronic systems depend on defined performance characteristics of the potentiometer. Potentiometer manufacturers define performance variations over various criteria, such as application temperature or the vibration environment. However, eventually all potentiometers succumb to some wear out and fail. When the potentiometer fails, the electronic system no longer receives the input that was controlled or monitored through the potentiometer. This can correspond to a loss of functionality in the device using the potentiometer because of the loss of electrical input from the monitored sensors or controls.

"Today, multiple approaches exist to address the eventual wear out and resulting failure of the potentiometer. One approach uses analysis and testing to demonstrate that the potentiometer will not fail over the service life of the device. In this case, the failure is not actively detected or mitigated in the application, however the robustness of the potentiometer is deemed adequate to avoid a loss of functionality in the device. Another approach uses detection means to determine when the potentiometer has failed, and to take some subsequent action. The action may include alerting the user, or entering a safe state such as shutting down the device.

"Prior methods of detecting potentiometer failure exist. However the known methods involve overhead and cost, including the need for additional physical components, which are not suitable for all applications. Known methods also include monitoring characteristics of the potentiometer, which may be important in some applications, but not important in others. An example application with constraints on component cost that is impacted by specific failure modes of the potentiometer is an electronic motor overload relay.

"In such an electronic motor overload relay, a potentiometer may be used as a voltage divider, where the divided voltage is determined by the position of an adjustment dial for a user interface to set the motor full load current parameter for the device. When the potentiometer is used as a voltage divider in this application, changes in some parameters of the potentiometer during the motor life such as change in the resistance value over temperature, do not affect the performance of the potentiometer in the device. However, a failure in which any connection within the potentiometer becomes open circuit, either between mechanical interfaces of the potentiometer subcomponents or between the potentiometer and the electronic board, can affect the performance of the device.

"Thus, a need exists for a potentiometer failure detection system that reliably detects the failure of a potentiometer. There is a further need for a system that uses components for the reading of a potentiometer to determine failures. There is also a need for a detection system that can identify the specific source of the failure for the device in which it is permissible or preferred to continue operating in the presence of certain distinguishable potentiometer failures."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "One disclosed example is a system to detect whether a potentiometer is in an open circuit condition. The system includes the potentiometer, which has a resistive element coupled between a voltage input and ground and an adjustable arm determining the resistance of the resistive element. A controller has a first driver output coupled to the voltage input of the potentiometer and a second driver output coupled to the adjustable arm. An analog to digital converter is also coupled to the adjustable arm to read the voltage of the potentiometer. The controller runs a routine to determine failure of the potentiometer. The routine sets the first driver output coupled to the voltage input of the potentiometer to a high value. A first sample voltage from the adjustable arm is read. It is determined whether the first sample voltage is between a high threshold and a low threshold value. If the first sample is outside the high and low threshold values, a potentiometer failure may be detected. The first driver output coupled to the voltage input of the potentiometer is then set to a low value. A voltage is then applied to the adjustable arm via the second driver output. A second voltage sample from the adjustable arm is read. Depending on whether the second sample is below an arm threshold value, a failure may be determined of the potentiometer.

"Thus, the detection system allows the detection of failure modes of the potentiometer, which are critical in particular applications, specifically an open circuit involving the potentiometer. The disclosed method does not add any cost in terms of additional components specific to the purpose of detecting the potentiometer failure. The use of a microcontroller to detect the open circuit condition in a circuit using a potentiometer is an additional advantage.

"Additional aspects will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

"The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

"FIG. 1A is a circuit diagram of a potentiometer failure detection system and an associated controller;

"FIG. 1B is the circuit diagram of the detection system in FIG. 1A showing potential points of failure in connections to the potentiometer resulting in potentiometer failure;

"FIG. 2A is a timing diagram showing the signals used in monitoring the potentiometer in FIG. 1A;

"FIG. 2B is a timing diagram showing the signals used in monitoring the potentiometer when no failure has occurred and the wiper arm is within a normal range of values;

"FIG. 3 is a flow diagram of the control algorithm executed by the microcontroller to detect failure of the potentiometer in FIG. 1A;

"FIG. 4A is a timing diagram showing signals in the detection system in FIG. 1A when a first type of failure is detected;

"FIG. 4B is a timing diagram showing the signals in the detection system when the wiper arm of the potentiometer is set low and therefore no failure has occurred;

"FIG. 4C is a timing diagram showing the signals in the detection system in FIG. 1A when a second type of failure is detected;

"FIG. 4D is a timing diagram showing the signals in the detection system when the wiper arm of the potentiometer is set high and therefore no failure has occurred; and

"FIG. 4E is a timing diagram showing the electrical signals in the detection system in FIG. 1A when a third type of failure is detected.

"While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims."

For more information, see this patent application: Jefferies, Kevin. Open Potentiometer Detection System. Filed December 31, 2012 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5670&p=114&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Electronics, Microcontroller, Schneider Electric Usa Inc.

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Source: Electronics Newsweekly


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