Analog Input

[rob@vems.co.uk]

Cool - let us know what the raw value is when you remove the resistor, we should be able to work out the equation from there.

[z0tya]

I have made the measurement. The result is half good half bad.
The range of the sensor is 250 mV to 4750 mV from 17 kPa to 216 kPa, with linear out.
On athmospheric pressure it shows 2400 mV.
I got this without serial resistor (the map sensor signal into the vemsgauge analog input):

The positive range is nearly linear, but the vacuum is unusable. The sensor can't pull the signal below 2400 mV, so unable to measure below athmospheric pressure. (without connected signal line the map sensor out is working properly of course).
I made another measurement without the sensor:
disconnected analog in (4v) megatune shows 1520
pull the ground (0V) shows 1040
pull up to 5V shows 1600
There is a breakpoint at 4V. Unfortunatelly I didn't have a variable resistor at hand to do more measuring point.
I think the reference voltage on the gauge input makes problem to use the analog input correctly.

[rob@vems.co.uk]

Thanks for that, I've not seen anything quite as concise and well researched for a while.
You will really need to post this information on the Wiki, I would suggest on this page:
http://www.vems.hu/wiki/index.php?page=AfreshTiny/AnalogInput

Posting what you have here may result in a positive response. 

[z0tya]

Ok! Thanks your very fast reply. I put the info on the wiki.

[z0tya]

I have made real logging last saturday with a bmw v8 kompressor. The analog input calibrated to show absolute pressure with this curve:

analog input curve 11 (165)  97
analog input curve 12 (180) 158
analog input curve 13 (195) 170
analog input curve 14 (210) 206

analog input calibration 32
analog input offset        0

This is the log file
http://www.vems.hu/files/MembersPage/ZoltanAlmasi/datalog200811151111forgatas.xls

The result is seems good. Only the rpm input has similar problem as Ranz here:
http://www.vems.co.uk/forum/index.php?topic=464.0

[webblaster]

hi, i still cant calibrate my 300 kpa sensor..
(http://shop.vems.hu/catalog/product_info.php?cPath=1_12&products_id=89)
is there a graph/chart for that sensor, too?
on athmospheric pressure, my DVM shows 2172 mv, but that doesn't fit in the chart, ive made up on the ranges (0,2v-4,8 and 20-300kpa)

[rob@vems.co.uk]

Theres a datasheet for the sensor here:
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-34/DSA-677433.pdf
And theres a graph on page 3 giving the voltage out.

[webblaster]

that sheet data is similar to the chart i've made up..
but why do i measure 2,171 V when no pressure is connected to the MAP sensor (my city is 55-100m above sea level)
that should mean, there is a pressure of apprx. 140 pka?! i don't think so

[gunni]

Can you check that your feed to the sensor is actually 5v?

[webblaster]

well the sensor has a 12v input and a 5v output..
and the input is connected to my car battery..
or what do you mean?

[rob@vems.co.uk]

Is this voltage being read with the MAP sensor connected to the Wideband gauge?

[webblaster]

yes..

[rob@vems.co.uk]

There is a pull-up on the gauge's input, if you disconnect it briefly you should see the same voltage as in the data sheet.
Then you'll be able to work out the voltage offset to add to that graph.

[z0tya]

This pullup is make troubles for everybody

[ranz]

My original audi bosch 200BAR MAP voltage did not change, was round connected or disconnected, no change on voltage. When voltage is affected you should use resistor (10kOhm?) because otherwise ecu is going to get wrong boost reading.