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Post Info TOPIC: Vcc stability for sensors.


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Vcc stability for sensors.


Has anyone logged the Vcc supply from the ECU?

I am interested in how stable this supply is. My guess is it is possibly a band gap linear voltage regulator, similar to the LM317 or LM340 series.

There's a picture of an exposed 07 600 ECU recently. I am sure you guys at least know what regulator they are using. I could work the drift out that way.

It should be low enough for what I am planning to do.

Another guess is that they rely on the stability of the voltage regulator and there is no feedback loop or compensation for drift. I.e. it is an open loop reference in respect of sensor and A/D operating points.



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more or less..

and because of this, ecu reads the Vcc sensor supply back and calculates the physical value depenting on factor, offset and depenting on Vcc.

 

Just look in datasheets of low cost sensors and you will know, what I mean



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Jochen, I am having trouble following you. I gather English is not your first language.

The ECU provides +5Vdc supply (Vcc) to the various sensors. The ECU doesn't read the Vcc supply back it is only an output.

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kwaka10r wrote:

Jochen, I am having trouble following you. I gather English is not your first language.

The ECU provides +5Vdc supply (Vcc) to the various sensors. The ECU doesn't read the Vcc supply back it is only an output.


 It is exactly like I worte.

ECU supplies sensors with + 5V (Vcc). This supply is more or less constant, normaly in a range of +/- 1%.

To have a correct mearsurement of a low cost sensor I need to know the exact Vcc, because sensor output depents on Vcc.

So ECU internaly measure its Vcc back, to be able to calculate the exact physical value of the sensor output depending on actual Vcc



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Jochen , thanks so much for your reply.

It would appear also that the air pressure sensors have quite a bit of variability (part to part) in output for the same input based on a table in the service manual. I'd say much more than the Vcc supply sensitivity.

I am wondering if anyone knows if or how the ECU program normalises this difference? After all there is no reference to calibrate against.

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For anyone interested.

I just finished logging the IAP and did some static tests on two other IAP/AP sensors (they're the same part on a lot of GSX-Rs) and I measured +/- 0.15%. It would seem that the IAP and AP sensors have very accurate absolute outputs.

I haven't check IP versus OP slope deviation or Vcc sensitivity, however I do believe that the sensors are going to be very closely matched unit to unit. I would love to know if there is a data sheet around to save me measuring or guessing this.

Based on this I am guessing these things run open loop WRT Vcc. It also confirms my doubts about these being low cost with the implication of a large variability between unit part. Also the SW and ECU could not possibly obtain barometric pressure any other way than the part having absolute accuracy or there was some calibration unit to unit from the production line. The latter certainly could not be the case as there is no calibration routine in any model GSX-R service manual.



-- Edited by kwaka10r on Wednesday 29th of August 2012 07:06:21 AM



-- Edited by kwaka10r on Wednesday 29th of August 2012 07:08:12 AM

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