Snap-on Tools Corporation

John C Sniegowski

Craig F Govekar

Michael B Meeker

Michael C Putrow

James R Piehl

Gary D Jonker

Dennis G Thibedeau

Ron D Geisler

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed and calculates and display spark plug burn time information derived from a single analog input signal, the data being displayed in both numerical and bar graph form. The measured burn time is the time that the ignition voltage signal is above a predetermined threshold level which is greater than the amplitude of the ringing portion of the ignition voltage signal.

Digital engine analyzer

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed. The engine calculates and displays real-time cylinder time balance information by calculating for each cylinder the cylinder time period from the firing of that cylinder to the firing of the next cylinder, storing the cylinder time values for each cylinder for a number of successive engine cycles, averaging the time period values for each cylinder over that number of engine cycles, calculating an overall average of the cylinder averages, calculating the percentage difference between each cylinder average and the overall average and then displaying the percentage differences in both numerical and bar graph form along with the overall average value.

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menudriven stored program control. The analyzer receives analog input signals from an engine being analyzed. Peak capture circuitry permits the display of a full cylinder period of a waveform, even though it contains very high frequency portions, by selectively switching between normal and high resolution modes. The circuitry samples the analog waveform at a very high rate and selects samples for display at a much slower display rate. The circuitry captures and stores the highest magnitude sample in each cylinder cycle by storing each sample only if its magnitude exceeds that of the previously stored sample. In the normal mode, at each display clock pulse the most recent sample is selected for display, irrespective of its magnitude. In the high resolution mode the stored peak value is selected for display at each display clock pulse.

Waveform peak capture circuit for digital engine analyzer

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed, digitizes the signals, captures the digital peak ignition voltage values for each cylinder and stores only these values for each cylinder over a number of successive engine cycles, and then simultaneously displays all the stored values for any one cylinder over a number of engine cycles to provide a historical display. Each peak value is stored twice and displayed twice to provide width to the value display and effectively produce a bar graph-type display.

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed. The analyzer is provided with a scanner interface, so that a scanner designed to read data from a vehicle on-board computer, can transfer this data to the analyzer for display on the analyzer oscilloscope. The analyzer processor, when operating in the scanner interface mode, operates under stored program control to reconfigure analyzer keyboard and soft key functions to duplicate scanner control functions, so that the scanner control functions can be effected from the analyzer.

A distributorless ignition interface unit for use with an engine analyzer for analyzing an internal combustion engine includes a processing circuit which responds to analog signals representing true and wasted firings for the cylinders of the engine under test to determine the number of cylinders of the engine and the polarity of the firing of each cylinder and to then characterize the engine by determining the order of the true and wasted firing signals produced during an engine cycle and for producing a parade pattern of true or wasted secondary signals for application to the engine analyzer.

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Kenosha, WI, United States of America

John C Sniegowski