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Converting analog sensor signal to digital reading

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Old Mar 3, 2017, 05:37 PM   #1
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Converting analog sensor signal to digital reading

Hi all,

I apologise for the very basic nature of the following questions

I've been through the evoscan website, and have found snippets of relevant information, but I'm still a little unsure how to proceed.

Normally I'd find the spec sheet of the individual sensor used, which normally has a formula for converting the 0-5 or 0-12V analog reading into a digital output (e.g. speed, temperature, etc.).

If the sensor spec sheet isn't available, how can I convert the sensor signal to a meaningful digital output? I've used generic (i.e. not designed for the evo) digital speed displays in the past, which just connected to the road speed signal wire and gave an accurate digital read out. Where is the logic for this conversion?

Is there a listing of the stock sensors, their anolog voltage range, and a formula for their conversion?

E.g.:

Coolant temperature: 0-12VDC, x*5.5 = Temperature F
O2 Sensor: 0-12VDC, x*2.4 = AFR

Similarly, are the ECU outputs documented anywhere? For example, the Tach signal out of the ECU.

Many thanks!

Jamie
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Old Mar 3, 2017, 09:56 PM   #2
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Quote:
Originally Posted by jars121 View Post

E.g.:

Coolant temperature: 0-12VDC, x*5.5 = Temperature F
O2 Sensor: 0-12VDC, x*2.4 = AFR

Similarly, are the ECU outputs documented anywhere? For example, the Tach signal out of the ECU.

Many thanks!

Jamie
Coolant sensors are thermistors.

They change resistance with temperature, there's different sorts.
The tach signal, that comes from the coil (from the PTU) , not the ECU.
It's a pulse.
Different computers code the signals in different ways.

No spec sheet is required, use a multimeter or oscilloscope.
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Old Mar 4, 2017, 10:40 PM   #3
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Quote:
Originally Posted by RightSaid fred View Post
Coolant sensors are thermistors.

They change resistance with temperature, there's different sorts.
The tach signal, that comes from the coil (from the PTU) , not the ECU.
It's a pulse.
Different computers code the signals in different ways.

No spec sheet is required, use a multimeter or oscilloscope.
Thanks for your input, it's greatly appreciated

Thermistors should be straight forward. I was under the impression the 'tach' signal itself was computer by the ECU from the crank and cam sensors, with the resulting signal being sent to the dash?
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