VR Sensor Sync Loss Scope Traces
Posted: Tue Feb 15, 2011 2:01 am
I am having a sync loss problem that we are trying to troubleshoot. The configuration is a 36-2 crankwheel with a Bosch IA-C type VR sensor. The sensor is similar to p/n 026121047 (http://www.urotuning.com/shop/crank-pos ... p-964.html) except it is 2-wire unshielded.
The problem would originally occur at 8000rpm, and would appear on a tooth logger as losing teeth. Instead of logging 34 teeth/missing teeth, the tooth count might be 32 or 33. Efforts to mitigate the problem included adding resistors to the vr+ leg. Addition of 90k Ohm resistor resulted in raising the rpm ceiling to over 10,000 rpm with only occasional sync loss. It also resulted in a reduction of peak-to-peak voltage from 44v to approximately 18v.
However encouraged I might be with the improved result, I am still concerned about the irregular scope traces. Whereas I would expect to see 34 well defined AC sine wave cycles/peaks, it almost appears as an alternating high peak/low peak for every other tooth.
Additionally, I am concerned about the how the signal completely deteriorates for 1-3 cycles during a sync loss event, as shown in the first and second traces. I am trying to fix the root cause as opposed to just treating the symptom. Perhaps the attached scope traces show a pattern that is familiar? I am thinking that the problem could be the result of any one or more of the following:
1) Electromagnetic Interference being picked up by the VR sensor cable
2) Ground issues
3) Sensor failure
Any help determining the root cause will be appreciated.
===============================
Here are the latest screen shots from today .
All scope signals were taken form the input of the VR into the box ( before the conditioner).
First one is a sync loss at 8000 rpm with no input resistor
Next one is much the same ,there seems to be alot of noise on the VR signal.
The last one was with 90k in series with the VR + and this was at 8500 with no sync loss , he was able to spin it to 10500 before it would loose sync now.
The problem would originally occur at 8000rpm, and would appear on a tooth logger as losing teeth. Instead of logging 34 teeth/missing teeth, the tooth count might be 32 or 33. Efforts to mitigate the problem included adding resistors to the vr+ leg. Addition of 90k Ohm resistor resulted in raising the rpm ceiling to over 10,000 rpm with only occasional sync loss. It also resulted in a reduction of peak-to-peak voltage from 44v to approximately 18v.
However encouraged I might be with the improved result, I am still concerned about the irregular scope traces. Whereas I would expect to see 34 well defined AC sine wave cycles/peaks, it almost appears as an alternating high peak/low peak for every other tooth.
Additionally, I am concerned about the how the signal completely deteriorates for 1-3 cycles during a sync loss event, as shown in the first and second traces. I am trying to fix the root cause as opposed to just treating the symptom. Perhaps the attached scope traces show a pattern that is familiar? I am thinking that the problem could be the result of any one or more of the following:
1) Electromagnetic Interference being picked up by the VR sensor cable
2) Ground issues
3) Sensor failure
Any help determining the root cause will be appreciated.
===============================
Here are the latest screen shots from today .
All scope signals were taken form the input of the VR into the box ( before the conditioner).
First one is a sync loss at 8000 rpm with no input resistor
Next one is much the same ,there seems to be alot of noise on the VR signal.
The last one was with 90k in series with the VR + and this was at 8500 with no sync loss , he was able to spin it to 10500 before it would loose sync now.