• Locked Locked
  • Replies 3 replies
  • Subscribers 23 subscribers
  • Views 2350 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPIC8101: resonant / flat-response knock sensor type

David Sobon
Prodigy 70 points
Other Parts Discussed in Thread: TPIC8101

I have tested TPIC8101 with the following sensors in a real environment (engine at 2000-4000 rpm, under heavy load):

* Nissan 22060-56S10 (resonant, 1 wire) - functions very well. many hours of testing with no issue.

* Nissan 22060-30P00 (flat-response, 2 wire) - functions very well, surprised it actually worked. A few hours of testing with no issue.

* Toyota 89615-22040 (resonant, 1 wire) - extremely noisy, very poor knock detection performance. Using voltage divider ratio of 22 somewhat helps, and increasing p2p voltage to maximum, but still noisy (false knock reading) than the above two sensors. Changing centre frequency does not help. This was tested under light-load conditions.

The above observations was made by graphing knock level per ignition event over time.

my question is:

1) which sensor type is supported / not supported and

2) "The TPIC8101 only works with the resonant type knock sensor. We do not offer a device that works with the non-resonant type. " -  http://e2e.ti.com/support/applications/automotive/f/26/t/118763.aspx - How did this conclusion come about?

Thanks.

  • TI__Mastermind 21821 points

    David,

    I do not have any experience with the flat-response knock sensors, but I believe that our device was designed with the intent to use with resonant type sensors because of how the analog front end is configured.

    These sensors are made to amplify their fundamental frequency when exposed to a knock. Our front end has a configurable band-pass filter designed to center around the sensors fundamental frequency. With that being said if you have had luck using a flat sensor i do not know of a reason you can't continue to use it. I will also check with the original apps engineer for this part that created all of the training and made the original comment saying it would only work with the resonant type. 

    Thanks,

    John

  • in reply to John Griffith
    Prodigy 70 points

    Problem with Toyota resonant sensor is now resolved.

    I wired the voltage divider to the wrong sensor input.

    Using voltage divider ratio of 4 now produces reasonable knock level output, although a ratio up to 8 may be needed to differentiate "background noise" from real knock.

    Comparing Toyota resonant signal with Nissan flat-response on Toyota engine now results in similar knock level output signal.

    Although it still leaves the question unanswered - why flat-response sensor was thought to not function with the TPIC8101.

  • in reply to David Sobon
    TI__Mastermind 21821 points

    David,

    I spoke with the applications engineer that supported the device previous to me, and he said that other customers have gotten it to work as well. Again, I think it just boils down to the device was not designed with the intent to work with non-resonant sensors, but from your results and others it appears that in some applications it will work.

    John