Electronic gauge transform

• US 5,325,314 A
• Filed: 09/11/1992
• Issued: 06/28/1994
• Est. Priority Date: 09/11/1992
• Status: Expired due to Term

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delco Electronics Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Hansen, Mark C., Nelson, James E., Chintyan, James R., Lippmann, Raymond, Schnars, Michael J.
• Primary Examiner(s): Teska, Kevin J.
• Application Number:
  US07/944,140
• Time in Patent Office: 655 Days
• Field of Search: 73/313, 73/308, 73/290, 73/430, 364/509, 364/510, 364/571.01-571.08, 364/562, 340/870.38, 340/644, 341/170
• US Class Current: 702/86
• CPC Class Codes: G01F 23/802 Particular electronic circuits for digital processing equipment

Abstract

An apparatus for applying a curve transfer function to an input signal comprises a first set of memory for storing values representing boundary points or distance differences along a curve of the transfer function, a second set of memory for storing slope values of lines connecting adjacent boundary points along the curve, a counter unit for maintaining a position count indicating position along the curve of the transfer function with respect to the stored boundary point values, an addressing unit, responsive to the position count, for selecting, from the second set of memory memory, the slope value corresponding to the position count, an accumulator for adding the selected slope value to an accumulator output value; and a comparator and data latch for determining when the accumulator output value corresponds to the input signal, and for selecting the corresponding accumulator output value as an output signal representing the application of the curve transfer function to the input signal.

Claims

1. An apparatus for applying a curve transfer function to a signal, comprising:

first counting means for periodically incrementing a comparison count signal in response to a clock signal;

comparison means for receiving an input signal and the comparison count and for outputting a comparison output signal at a time when the input signal equals the comparison count;

second counting means for periodically decrementing a curve position signal in response to the clock signal, wherein the presettable down counter is presettable to a boundary count signal;

accumulator means for periodically incrementing, by a slope increment signal, an accumulator output signal in response to the clock signal; and

means for outputting an output signal equal to the accumulator output signal at the time when the comparison output signal is output by the comparison means, wherein the output signal represents a curve transfer function applied to the input signal.

2. The apparatus set forth in claim 1, also comprising, memory means for supplying the slope increment signal to the accumulator means and a boundary count difference signal to the second counting means.

3. The apparatus set forth in claim 2, wherein, when the second counting means underflows, it outputs an underflow signal, wherein the apparatus also comprises third counting means, incrementing an address signal in response to the underflow signal, for addressing the memory means.

4. The apparatus set forth in claim 3, also comprising means for periodically applying a reset signal to the accumulator means and the first, second and third counting means so that the accumulator means and the counters are periodically reset and so that the output signal is periodically updated.

5. The apparatus set forth in claim 2, wherein the memory means contains pairs of memory address locations, each pair of memory address locations containing values for the boundary count difference signal and a slope increment signal, so that when each memory address location is addressed, the value for the boundary count signal contained therein is supplied to the second counting means and the value for the slope increment signal contained therein is supplied to the accumulator means.

6. An apparatus for compensating for nonlinearities in a parameter display system, comprising:

a first counter receiving a reset signal and a clock signal comprising a series of pulses, resetting to zero when the reset signal is received and incrementing a comparison count signal with every pulse of the clock signal;

a comparator with first and second comparison inputs, the first comparison input receiving an input signal and the second comparison input receiving the comparison count signal, the comparator providing a comparison output signal when the input signal equals the comparison count signal;

a first set of memory containing curve boundary signals;

a second set of memory containing slope increment signals;

a second counter coupled to the first and second sets of memory and receiving the clock and reset signals, the second counter containing a curve position count being presettable to the boundary signal received from the first set of memory, decrementing the curve position count signal with every pulse of the clock signal, providing an underflow signal when the presettable down counter underflows and resetting with every underflow signal to a count equal to the boundary signal supplied by the first set of memory;

a third counter, coupled to the first and second sets of memory to address the first and second sets of memory with an address count signal, receiving the underflow and the reset signals, incrementing the address count signal with every underflow signal and resetting with every reset signal;

an accumulator receiving the clock signal and the reset signal and coupled to the second set of memory to receive the slope increment signal therefrom, the accumulator resetting to zero in response to the reset signal and, with every pulse of the clock signal, periodically incrementing, by the slope increment signal, an accumulator output signal; and

a data latch coupled to the comparator and to the accumulator, the data latch receiving the comparison output signal from the comparator, latching in the accumulator output signal in response to the comparison output signal, and providing the latched comparison output signal as a circuit output signal, thereby compensating for nonlinearities of the system.

7. The apparatus set forth in claim 6, also comprising means for providing the clock signal and means for periodically providing the reset signal.

8. The apparatus set forth in claim 7 wherein the first counter is an eight bit counter and the reset signal has a frequency at least 256 times slower than a frequency of the clock signal.

9. The apparatus set forth in claim 6, also comprising a display device coupled to the data latch, linearly displaying a measurement of the parameter.

10. The apparatus set forth in claim 9, wherein the display device is an analog gauge.

11. An apparatus for applying a curve transfer function to an input signal, comprising:

first memory means for storing values representing boundary points along a curve of the transfer function;

second memory means for storing slope values of lines connecting adjacent boundary points along the curve;

counter means for maintaining a position count indicating position along the curve of the transfer function with respect to the stored boundary point values;

means, responsive to the position count, for selecting, from the second memory means, the slope value corresponding to the position count;

accumulator means for adding the selected slope value to an accumulator output value; and

means for determining when the accumulator output value corresponds to the input signal, and for selecting the corresponding accumulator output value as an output signal representing the application of the curve transfer function to the input signal.

12. An apparatus comprising:

means for receiving an input signal;

memory means for storing (i) a first set of addressable data comprising points along a curve, and (ii) a second set of addressable data comprising slope increments of lines connecting consecutive points along the curve;

a counter with an output count incremented in response to a clock pulse;

a first comparator with a first input coupled to the output count and a second input coupled to the input signal, the first comparator comparing the output count to the input signal and providing a first comparison output in response;

means, responsive to the output count and a second comparison output, for addressing the memory means and for selecting a point from the first set of addressable data;

the second comparator with a first input coupled to the output count and a second input coupled to the memory means, the second comparator comparing the selected point to the count output and providing the second comparison output in response;

means, responsive to the output count for addressing the memory means and for selecting a slope increment from the second set of data;

means for adding the selected slope increment to an accumulator output;

an accumulator providing the accumulator output; and

means for outputting the accumulator output responsive to the first comparison output as a piece-wise linear approximation of a transform of the input signal.

13. An apparatus comprising:

means for receiving an input signal;

memory means for storing first and second sets of addressable data, the first set of data comprising a set of distances along a curve and the second set of data comprising slope increments of lines connecting consecutive points along the curve;

means for maintaining a position count along the curve;

means for addressing the memory and selecting from the first set of addressable data one data point responsive to the position count means and for selecting from the second set of addressable data one slope increment responsive to the position count means and the selected data point;

means for adding the selected slope increment to an accumulated value; and

means for outputting the accumulated value when the position count equals the input signal, whereby the output accumulated value equals a piece-wise linear approximation of a transform of the input signal.

14. The apparatus set forth in claim 13, also comprising:

means for sensing a level of fuel in a fuel tank and for providing the input signal responsive thereto; and

means for displaying a level of fuel in the fuel tank responsive to the output accumulated value, wherein the display means linearly displays the level of fuel in the tank.

15. A paramter measurement and display apparatus, comprising:

means for sensing a level of a parameter and for developing a level signal;

memory means for storing boundary point values and slope values between the boundary point values representing a piece-wise linear approximateion of a nonlinear curve transfer function characterizing nonlinearities inherent in the parameter and display apparatus;

means for transforming the level signal to develop a resulting output signal based upon the stored boundary point values and the slope values between the boundary point values to compensate for the inherent nonlinearities of the apparatus; and

means for driving a display in response to the output signal.