miatauser884

iTrader: (11)

I tried to calibrate my MPX5700

http://www.freescale.com/files/senso...et/MPX5700.pdf

How do I get this new sensor to work properly?

UPDATE: The bright blue box in the above link has all of the information that is needed to calibrate the MAP sensor.

I finally figured out what was going on. In my attempt to extrapolate to the min and max values in tunerstudio I did not realize that negative values are ok to use. Since this MAP sensor goes from 0-700 kpa from .2 - 4.7v, you have to find out what the voltage is at 0v and 5v to setup the linear table. This makes the kpa value that corresponds with 0v = -31.1kpa, and 777kpa for 5v. I adjusted it slightly so that it gave me the actually pressure according to the NOAA and corrected for altitude at my location. Actual values yielded a 2.2% error, which is within the spec tolerance of +/- 2.5%. Hopefully this error is also linear and I just permanently corrected for it. I ended up with -31.1kpa=0V and 760kpa = 5V.

In case anyone else runs into this problem. You need to find the operating range of the MAP sensor in order to calculate the V/kpa.
In this case min. = .2V and max = 4.7V. 4.7V-.2V=4.5V operating range. 4.5V/700 = .0064V/kpa. so .2V/.0064V/kpa = 31.1 kpa and .5V/.0064 V/kpa = 77.7kpa Now find the 0V and 5V values. Need to subtract .2V from min MAP sensor value to get to value at zero volts. 0kpa - 31.1 kpa = -31.1kpa. To get to 5V from 4.5V you need to add .5V or 77.7 kpa to max value. 700kpa +77.7 kpa = 777.7 kpa.

Braineack

iTrader: (62)

thanks! I didn't feel like thinking today.

DIYAutoTune

Awesome info.

Braineack

iTrader: (62)

Yeah, I had this datasheet open on saturday and remember someone else that used this sensor already did the work for me and posted. Saved me brain power.

DIYAutoTune

Can i see Said data sheet?

Braineack

iTrader: (62)

It's posted in the first post.


but basically:

MPX5700 Series
15 to 700 kPa (2.18 to 101.5 psi)
0.2 to 4.7 V Output

and the MS is looking for data points at 0 and 5v, where only .2v and 4.7v is known. If you plug in 15kPa at 0v and 700kPa at 5v, you read ~120kPa atomspheric. So that extra .5v of range it's looking for is really imporant to figure out, and i was too lazy to figure out those datapoints myself.

Leafy

iTrader: (1)

Holy crap, a 7 bar map sensor. Now you really can run ALLOFIT.

Braineack

iTrader: (62)

if all of it = ~87psi, then yeah.

This sensor costs roughly $18 plus shipping, it's much more cost effective to run over 22psi than the 4-bar map-daddy at $65.

If you dont need barometric corrections, then it's the best sensor to replace the 2.5bar with, since it's phyically the same thing. If you need Barometric corrections, and run ms2 or ms3, then you could retain the 2.5bar as your baro sensor; the sensors dont have to be identical.

DIYAutoTune

thanks