Duty Cycle Oscilloscope Test Question

[jessem]

Hi guys, I was trying to set the mixture on my 1980 Porsche 911 SC using an oscilloscope. I'm getting a big dip on the graph. Please see the attached photo. Any idea what this could mean? It's my first time using this tool so I'm not familiar with what all the numbers mean. Any help would be greatly appreciated. Thanks!

[mysocal911]

Originally Posted by jessem

Hi guys, I was trying to set the mixture on my 1980 Porsche 911 SC using an oscilloscope. I'm getting a big dip on the graph. Please see the attached photo. Any idea what this could mean? It's my first time using this tool so I'm not familiar with what all the numbers mean. Any help would be greatly appreciated. Thanks!

That's normal, it's just frequency valve being switched-off, i.e. the inductive discharge voltage spike - like an ignition coil.

[jessem]

Oh really? All the photos I've seen show squared off graphs.

[yelcab1]

Let me ask an obvious, where did you attach the probes?

An O2 sensor cannot generate Vmax of 9.32V, or switch at 73 times per second.

[mysocal911]

Originally Posted by jessem

Oh really? All the photos I've seen show squared off graphs.

Did you not fully read the post where it describes the signal as the FREQUENCY VALVE signal??????