Hall Effect Cam Sensor

Hi guys, i'm new here and i've been watching videos for the past few weeks to help with my university course in motorsport engineering.

I've attached a picture of a Hall Effect Camshaft Sensor waveform, I have to identify the incorrect signal and explain how it would effect engine running.

Can anyone help? I'm aware that it doesn't say what vehicle is being tested and my tutor isn't able to give me any help on it, so this is why i'm here.

Thanks

Assuming the blue trace is the sensor power feed, and the red trace is the sensor signal, I would be looking into the charging system. It looks like a lot of A/C ripple. The sensors is functioning and has no problem pulling the signal to ground.

This was my assumption also, the information I gave was literally all I was given so I thought the blue was either power feed or it was another sensor with no trace of top dead centre.

Can I ask what effect the ripple would have on the car?

Am I also right in saying that the voltage on the right is off too? Or is that normal? As I thought cam sensors were supposed to switch from 0v to 5v.

I don't suppose you have the Pico file available to share? Not that it's needed, just makes analysis easier. I know there's no vehicle identified, and that's fine. But it would help to know what specifically is being measured on the blue trace. B+?

My first guess was a tremendous amount of AC ripple in the alternator output? But the frequency is way too low for a running engine. The engine is cranking? But your tutor asked how it'd impact engine RUNNING. Besides, the compression valleys are irregular.

If the blue trace is B+ then it'd impact... Everything. :silly: Anything and everything that depends on steady voltage to operate correctly.

Maybe the bigger question is SHOULD we be helping you? :silly: I want to help! But I also don't want to screw with your instructors teachings.

Chad is on the right path but also the power wire (5v ref) to the sensor would need to be looked at for a short to power. This would/could cause multiple issues as fuel injectors firing and ignition firing. Along with possible damage to engine computer.

I don't unfortunately, i've just print screened the Appendix I was given.
I have asked my tutor what the blue trace represents and he said he can't help me... which was nice..

The assignment says "Using the waveform in Appendix 3, identify the incorrect signal and discuss the likely effect on engine running" this doesn't really help either does it lol.

Can I ask what B+ is? Is it the voltage the alternator is supplying?

Honestly i'm at the stage now where I need as much help as I can get, I have my deadline in a week and the course and tutor are less than helpful.

david.wainwright wrote: Can I ask what effect the ripple would have on the car?

A/C ripple can play havoc with the electrical system. It can cause false high/low thresholds, especially in VR sensors that produce an A/C sine-wave.

Am I also right in saying that the voltage on the right is off too? Or is that normal? As I thought cam sensors were supposed to switch from 0v to 5v.

Without more information, it's hard to say, for sure. That's where SI (Service Information) comes in. Hall-Effect sensors can operate in a wide range of voltages. But, I have never seen a hall-effect cam signal (that wasn't bad) that was not a clean square-wave.

Thank you for your reply, it's really appreciated. So the A/C ripple could cause the voltage to be so high on the cam sensor?

All I was taught was that the waveform should be square and none erratic, nothing was said about if they weren't.

david.wainwright wrote: I don't unfortunately, i've just print screened the Appendix I was given.
I have asked my tutor what the blue trace represents and he said he can't help me... which was nice..

...

The assignment says "Using the waveform in Appendix 3, identify the incorrect signal and discuss the likely effect on engine running" this doesn't really help either does it lol.

Nice. :lol: :silly:

Can I ask what B+ is? Is it the voltage the alternator is supplying?

In this context, I meant it as voltage at the battery directly. DVOM/DMM connected across the battery posts.

Honestly i'm at the stage now where I need as much help as I can get, I have my deadline in a week and the course and tutor are less than helpful.

Welp, you're doing better than I did! I always waited until the night before stuff was due to get my act together. :lol:

In this context, I'm gonna stick with alternator problem. Failed diode in the rectifier bridge, failed regulator, whatever. Depending on the car, I'd expect misfiring, hesitiation, rough running, and/or multiple DTC's due to fluctuating B+ voltage.