Kdi Precision Products, Inc.

Kdi Corporation, Inc.

Alan R Hannan

Thomas M Nickolin

William E Atkinson

Ted W Lewis

J Jacob Noble

Bryan H McQuitty

Raymond V Onley

A liquid level sensor for detecting when an upper level of a liquid in a reservoir has reached a predetermined or critical point in the reservoir. The sensor includes a first input plate and a second input plate disposed concentrically relative to the first input plate. Each of the input plates are further of a shape such that an imaginary line extending through the centroid of the first input plate divides each of the first and second input plates approximately in half. An output or receiver plate is positioned closely adjacent the two input plates. The input plates are further disposed in the reservoir such that the centroid is at the predetermined or critical level in the reservoir. The two input plates are alternately electrically excited and the signals coupled to the output plate are detected and repeatedly compared against one another. The output signals will differ in magnitude because of the difference in the dielectric constant of air and the liquid in the reservoir. As the liquid level in the reservoir approaches the predetermined or critical point, the output signals coupled onto the output plate begin approaching one another. When the liquid level reaches the predetermined or critical point, the output signals are approximately equal in magnitude. A microcontroller detects this condition and generates a signal in response thereto. The performance or accuracy of the sensor is independent of changes in the dielectric constant of the fluid and, in some cases, is not affected by tilting or other changes in the orientation of the reservoir which might otherwise affect the accuracy of measurements taken by other forms of liquid level sensing devices.

Liquid level point switch sensor

A digital liquid level sensing apparatus for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array including a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of a fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages. The controller converts each of the peak voltage signals into a corresponding digital value and stores each of the digital values in an on-board memory. The controller then sequentially compares each of the values against at least one predetermined reference value indicative of an output produced by an input plate disposed in air until a predetermined difference is detected between the reference value and any one of the stored digital values. This indicates a predetermined difference in the dielectric, thus indicating that a corresponding input plate is at least partially submerged in fluid.

Digital liquid level sensing apparatus

A digital liquid level sensing apparatus for detecting variations in the dielectric of a substance being sensed, to thereby provide a signal indicative of the level of the liquid being sensed in relation to a known full level. The apparatus includes a reservoir having an output plate and an input plate assembly associated therewith. The input plate assembly includes a plurality of independently electrically excitable input plates which transmit a signal through the liquid being sensed to the output plate. The signals from the output plate are processed and a determination is made as to the level of liquid in the reservoir relative to a known full level. If the input plate assembly is located against the exterior surface of one wall of the reservoir, then both of the interior and exterior portions of that particular wall should be devoid of any metallic surface. In an alternative embodiment, a discardable interior reservoir is provided which fits nestably within the reservoir of the sensor. The interior reservoir is particularly useful for measuring water-based bodily fluids such as urine, where it may be desirable to discard just the reservoir after use.

An apparatus adapted to be coupled between a keyboard and a computer to enable a user to define desired keys as coded keys which are associated with MACROS defined by the user. The apparatus includes a microcontroller and an electrically erasable, programmable read only memory (EEPROM) which monitors codes transmitted from the keyboard and is placed in a programming mode when a predetermined program code is received from the keyboard. Once in the program mode, the next key depressed by the user is denoted as a coded key and the following keys depressed by the user are designated as a user programmed MACRO associated with the coded key. The apparatus stores this information in the EEPROM and thereafter when the coded key is depressed by the user the associated MACRO is generated and transmitted to the computer. The apparatus forms a very compact, relatively inexpensive means for enabling conventional keyboards to function as programmable keyboards. In an alternative preferred embodiment, editing and creation of the MACROS can be accomplished by receiving information from the computer through the use of a software program which enables the user to more conveniently enter and exit the programming mode, as well as make necessary edits to previously stored MACROS.

Programmable keyboard and method therefor

A digital liquid level sensing apparatus and method for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array which is disposed in a fluid to be measured and which includes a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of the fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages. The controller converts each of the peak voltage signals into a corresponding digital value and stores each of the digital values in an on-board memory. The controller then sequentially compares each of the values against at least one predetermined reference value indicative of an output produced by an input plate disposed in air until a predetermined difference is detected between the reference value and any one of the stored digital values. This indicates a predetermined difference in the dielectric, thus indicating that a corresponding input plate is at least partially submerged in fluid.

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Cincinnati, OH, United States of America

Alan R Hannan