Single sensor engine analyzer with noise rejection and automatic triggering circuit

In an improved apparatus for analyzing the operation of a multiple cylinder internal combustion engine wherein plug firings to obtain cylinder ignition are displayed on a cathode ray tube and engine timing is determined by driving a timing light in synchronism with cylinder ignition, the improvement comprising:

• a first sensor means adapted for connection to the primary winding of the engine's ignition coil for sensing the plug firings of all the cylinders in said engine;
• a second sensor means adapted for connection to the secondary winding of the engine ignition coil for sensing the plug firings of all the cylinders in said engine;
• a first means responsive to said first sensor means for generating timing control signals representative of cylinder ignition;
• a second means responsive to said second sensor means for generating timing control signals representative of cylinder ignition;
• and,
• selector means adapted for receiving the timing control signals from said first and second timing control signal generating means and generating timing control signals in response to the first in time control signals received from said first and second timing control signal generating means.