Coil - Tach Signal Question/Concern

[Exolis]

So I brought home an Oscilloscope from work last night to play around with and see what some of these signals look like in an old system like this. Anyways, I did a quick measurement of the Tach signal coming from the Coil(the grey wire via Colored Wire Diagram) and noticed there is a Large Voltage Spike coming from that. I know it being a big inductor, it's going to give a large voltage for the Spark Plugs. However, this goes to things such as the RPM Relay, Idle Speed, Ign ECU and Tachometer. I haven't noticed any odd behavior in the tach, but with the large/quick voltage spike going to the other components, I feel like it is too high for those components to handle.

So my question is if this is normal for old systems like this? Or should I be looking to buy a new Coil?

[Farrar]

Could be noise from other stuff in the engine compartment. Did you try checking the signal where it goes to the ignition ECU? Might be a bit cleaner. Same wire color, I believe.

[Ron]

Typical Tach Wave

18669

[Exolis]

I did not measure near Module. Didn't have too much time to do all the measurements I wanted to do. Planned on doing more last weekend, but was busy. One of these weekends I'll do more indepth measurements and save them.

Also, that picture is pretty similar to what I saw. Where the lower voltage part seemed pretty similar to a Duty Cycle and got shorter for Higher RPM. Was pretty interesting to watch. Main purpose was to watch the Idle Motor, but nothing too exciting about that.

[Bitsyncmaster]

Yes that spike is normal. I remember it peaking at 150 volts when I checked it. All the circuits that use that signal have to handle that large spike. Actually the original RPM relay uses that spike as it's trigger (it will not work without the spike).