Author Topic: Wheel speed maximim frequency?  (Read 5634 times)

Offline dnb

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Wheel speed maximim frequency?
« on: May 21, 2012, 12:58:13 am »
Has anyone found the wheel speed signal can't cope with a frequency higher than 1096Hz?  On my bench test rig I can get the wheel speed to function, but unless I limit the input frequency to less than 1096Hz I get aliasing effects followed by zero speed displayed.  The divider and pulses per 100km/h work as expected.

The divider doesn't help because it's implemented after the pulse counter stage, so it just reduces the range of speed displayed in VEMStune.

I really need something to work to at least 4kHz.  Am I missing something in the config or do I have to build a hardware divider for the input?

Thanks

Offline rob@vems.co.uk

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Re: Wheel speed maximim frequency?
« Reply #1 on: May 22, 2012, 11:53:04 am »
I would hazard a guess that its the max speed you'll see as the speed sensor is connected to the IO that was used for keyboard input, I'm guessing a hardware divider is required.

Offline GintsK

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Re: Wheel speed maximim frequency?
« Reply #2 on: May 22, 2012, 08:12:12 pm »
Did you scoped input pin? Could be that low-pass filter cut amplitude. Just a guess.

Gints

Offline dnb

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Re: Wheel speed maximim frequency?
« Reply #3 on: May 22, 2012, 10:47:25 pm »
I did scope the input to the ECU.  It remained at a good signal level all the way to 5kHz.  I'm using the speed signal to control the epas system too.