Engine analyzer waveform display with a buffer region

• US 5,160,892 A
• Filed: 10/05/1990
• Issued: 11/03/1992
• Est. Priority Date: 10/05/1990
• Status: Expired due to Term

• Current Assignee: GSLE Subco, LLC (SPX Corporation)
• Original Assignee: Bear Automotive Service Equipment Company (SPX Corporation)
• Inventors: Sparacino, Steven J., Burgess, Robert T., Makhija, Surender K.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US07/593,154
• Time in Patent Office: 760 Days
• Field of Search: 324/378, 324/379, 324/384, 364/424.03, 364/424.04, 364/431.03, 364/551.01, 73/117.3
• US Class Current: 324/379
• CPC Class Codes: F02P 17/08 using a cathode-ray oscilloscope F02P17/06 takes precedence

Abstract

An engine analyzer for an internal combustion engine includes an analog-to-digital (A/D) converter which digitizes an analog input waveform representing, for example, a secondary or primary voltage waveform of the ignition coil of the internal combustion engine. The sampling rate of the analog digital converter is determined by dividing the waveform time period by the desired number of samples. An adjustment factor C is used to provide a buffer period during the sampling period of the waveform. A display for displaying the waveform has a buffer region which corresponds to the buffer period. Thus, a variation in the speed of the engine which causes the engine to slow down and extends the period of the engine waveform does not cause a loss of data collected from the waveform because the buffer period provides a margin of error.

Claims

1. A display, for an engine test system, comprising:

means for providing a periodic analog input waveform representative of operation of an internal combustion engine, the waveform having a period which varies as a function of the engine speed;

analog to digital converter means for sampling the analog input waveform periodically at a data sampling rate and converting each sample to a digital value representative of an analog value of the analog input signal;

display means for displaying a simulated visual representation based upon digital values from the analog to digital converter, the simulated visual display being representative of operation of the internal combustion engine; and

means for determining the data sampling rate of the analog to digital converter as a function of engine speed, an adjustment factor, a maximum number of data points, a number of cylinders of the internal combustion engine, and a total firing time of a firing cycle of the internal combustion engine.

2. The display of claim 1 wherein during a firing cycle of the internal combustion engine the data sampling rate provides about ten percent less data samples than the maximum number of data points.

3. The display of claim 1 wherein the display means includes a primary display for displaying the simulated visual representation of a function of the internal combustion engine and a buffer region for displaying portions of the visual representation which exceed boundaries of the primary display region.

4. The display of claim 3 wherein the buffer region has a display capacity which is about ten percent of a display capacity of the primary display region.

5. The display of claim 4 wherein the display capacity of the buffer region is a function of the adjustment factor.

6. A display, for an internal combustion engine, comprising:

means for providing a periodic analog input waveform representative of operation of an internal combustion engine, the waveform having a period which varies as a function of the engine speed;

analog to digital converter means for sampling the analog input waveform periodically at a data sampling rate and converting each sample to a digital value representative of an analog value of the analog input signal;

display means for displaying a simulated visual representation based upon values from the analog to digital converter, the simulated visual display being representative of a function of the internal combustion engine, the display means including a primary display region for displaying the function of the internal combustion engine, the primary display region having display boundaries, and a buffer display region for displaying portions of the simulated visual display which exceed the display boundaries of the primary display region; and

means for determining the data sampling rate of the analog to digital converter as a function of engine speed, a maximum number of data points, a number of cylinders of the internal combustion engine, a total firing time of a firing cycle of the internal combustion engine and an adjustment factor.

7. The display of claim 6 wherein during a firing cycle of the internal combustion engine the data sampling rate provides about ten percent less data samples than the maximum number of data samples.

8. The display of claim 6 wherein the buffer display region has a display capacity which is about ten percent of a display capacity of the primary display region.

9. The display of claim 7 wherein the display capacity of the buffer display region is a function of an adjustment factor used to adjust the data sampling rate.

10. A method of sampling data, in an internal combustion engine testing system, comprising:

measuring a firing time of a cylinder of an internal combustion engine;

calculating a sampling time based upon the firing time, a predetermined number of data samples to be taken and a buffer period;

measuring a periodic analog waveform representative of operation of the internal combustion engine;

converting the analog waveform to a digital waveform at a sampling rate determined by the sampling time period; and

displaying a visual display representative of a function of the internal combustion engine based upon the digital waveform wherein the buffer period provides a buffer region in the display and the buffer region is about ten percent of the predetermined number of data samples, to accommodate variation in a total firing time of a cylinder.

11. The method of claim 10 wherein calculating a sampling time period comprises dividing a time period of a firing cycle of the internal combustion engine by a number of cylinders in the engine and a predetermined number of data points and multiplying by an adjustment factor.

12. A display, for an engine test system, comprising:

means for providing a periodic analog input waveform representative of operation of an internal combustion engine, the waveform having a period which varies as a function of the engine speed;

analog to digital converter means for sampling the analog input waveform periodically at a data sampling rate and converting each sample to a digital value representative of an analog value of the analog input signal;

display means for displaying a simulated visual representation based upon digital values from the analog to digital converter, the simulated visual display being representative of operation of the internal combustion engine, including a primary display for displaying the simulated visual representation as a function of the internal combustion engine and a buffer region for displaying portions of the visual representation which exceed boundaries of the primary display region; and

means for determining the data sampling rate of the analog to digital converter as a function of engine speed and an adjustment factor.

13. The display of claim 12 wherein the means for determining the data sampling rate comprises means for determining the data sampling rate as a function of a maximum number of data points, a number of cylinders of the internal combustion engine, a total firing time of a firing cycle of the internal combustion engine and the adjustment factor.

14. The display of claim 13 wherein during a firing cycle of the internal combustion engine the data sampling rate provides about ten percent less data samples than the maximum number of data points.

15. The display of claim 12 wherein the buffer region has a display capacity which is about ten percent of a display capacity of the primary display region.

16. The display of claim 15 wherein the display capacity of the buffer region is a function of the adjustment factor.

17. A display for an internal combustion engine, comprising:

means for providing a periodic analog input waveform representative of operation of an internal combustion engine, the waveform having a period which varies as a function of the engine speed;

analog to digital converter means for sampling the analog input waveform periodically at a data sampling rate and converting each sample to a digital value representative of an analog value of the analog input signal;

display means for displaying a simulated visual representation based upon values from the analog to digital converter, the simulated visual display being representative of a function of the internal combustion engine, the display means including a primary display region for displaying the function of the internal combustion engine, the primary display region having display boundaries, and a buffer display region for displaying portions of the simulated visual display which exceed the display boundaries of the primary display region wherein the buffer display region has a display capacity which is about ten percent of a display capacity of the primary display region; and

means for determining the data sampling rate of the analog to digital converter as a function of engine speed.

18. The display of claim 17 wherein the means for determining the date sampling rate comprises means for determining the data sampling rate as a function of a maximum number of data points, a number of cylinders of the internal combustion engine, a total firing time of a firing cycle of the internal combustion engine and an adjustment factor.

19. The display of claim 18 wherein during a firing cycle of the internal combustion engine the data sampling rate provides about ten percent less data samples than the maximum number of data points.

20. The display of claim 17 wherein the display capacity of the buffer display region is a function of an adjustment factor used to adjust the data sampling rate.

21. A method of sampling data, in an internal combustion engine testing system, comprising:

measuring a firing time of a cylinder of an internal combustion engine;

calculating a sampling time period by dividing a time period of a firing cycle of the internal combustion engine by a number of cylinders in the engine and a predetermined number of data points and multiplying by an adjustment factor;

measuring a periodic analog waveform representative of operation of the internal combustion engine;

converting the analog waveform to a digital waveform at a sampling rate determined by the sampling time period; and

displaying a visual display representative of a function of the internal combustion engine based upon the digital waveform wherein the buffer period provides a buffer region in the display, to accommodate variation in a total firing time of a cylinder.

22. The method of claim 21 wherein the buffer region is about ten percent of the predetermined number of data samples.