4bar bosch map sensor calibration

Other Hardware Sensors
1

Hello guys!

Iam new to this forum so i have got a question about an original bosch vw sensor it a 4 bar map sensor with temp metering aswell(03k906051; bosch number; 0281006060)
So my problem is that i got the pinouts 1;gnd 2; temp out 3; +5v supply 4; map signal
So if i just connect +5 and gnd and wit multi meter i measure number 4th pin thats map out i got 1.69v.
But i made a tube so i can add boost and watch signal voltage as you can see readings in kpa so 100kpa is 1 bar.i got 4 bar map sensor but its only reading 1.8 1.9 bar with 4.91v but if i add more boost wont read so its max out at maybe 2 bar boost so why is that a 4 bar then or maybe i did some thing wrong..if anyone can help me!

Thanks Ricsi!!

2

Pressure test code, assuming you use an Uno or Mega.
Leo..

float pressure;

void setup() {
  Serial.begin(9600);
}

void loop() {
  pressure = analogRead(A0) * 0.4345; // read and convert
  
  Serial.print("Pressure is: "); // print
  Serial.print(pressure, 1);
  Serial.println(" kPa");
  
  delay(250); // remove delay when combined with other code
}
3

Thank you for reading this topic,its a good informacion for me but i have problem with only the sensor itself so i can read the sensor values correctly i tried 2 more sensors all of them bosch 4 bar and one bosch 3 bap tmap sensor its a 4 wire sensor but when i connect the wires and measure map output signal voltage it starts from 1.68v and when you give it pressure it works but the 4 bar sensor max out at 2 bar real pressure so my question is what iam missing ? Unfortunatelly i dont have any data about this specified sensor maybe someone got and could share with me.

Thanks Ricsi!

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4

I only could find a pressure graph for "bosch number; 0281006060" on the net.
When powered with 5volt, it should output 0.5volt@50kPa and 4.5volt@400kPa.
My maths line is based on that.
Leo..

5

Yes but if i just connect the electrical wires and it shows 1.68v

6

So 1.68volt without pressure, and ...

Seems you have to make your own pressure/voltage graph.
Then you (we) can change that into a maths formula.
Leo..

7

Yes but i dont uderstand that i have a 4 bar map sensor witch is 1bar pressure from the atmosfere and 3 bar boost,so i should see up to 3bar boost so thats why its a 4 bar sensor
i tested 5 sensor two 4 bar one 3 bar and 2 other sensor all of them are the same so when you just connect 5V and ground and measure the map sensor signal voltage output i got 1,6-1,7V withouth boost....when i give pressure the nubers are goint to rise but if i reach 2bar boost the sensor cant read more it maxes out 4.97V

8

Here is one sensor its not the same that i used its a 3 bar one,as you can see on the diagramm output voltage starts from 0,4V but mine start from 1,6V.....so the sensor measure the atmosferic pressure witch is not a problem but how can i see 3 bar really pressure on the voltage output....beacuse if its starts from 0,4V and goes up to 4,65 then it can show me 3 bar of boost just why does it start at 1,6V? :slight_smile:

bost.png
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9

With an 'offset' and 'gain' in the maths formula you can display whatever you want,
But you can't do anything about a 'clipping' sensor (sensor can't output more than 5volt).

Know nothing about those sensors, but common pressure sensors are usually rated between 0.5volt and 4.5volt.
Here is the formula that can work with the 'low' value (at 0.5volt), and 'top' value (at 4.5volt).
x.xx is the number to display at 4.5volt, e.g. 4.0 for a 4bar or 400.0 for a 400kPa sensor.

pressure = (rawValue - offset) * x.xx / (fullScale - offset);

You only have to tweak the fixed 'offset' and 'fullscale' A/D values, to calibrate the sensor.
See (untested) example.
Leo..

int rawValue; // A/D readings
int offset = 102; // zero pressure adjust
int fullScale = 922; // max pressure (span) adjust
float pressure; // final pressure

void setup() {
  Serial.begin(9600);
}

void loop() {
  rawValue = analogRead(A0);
  pressure = (rawValue - offset) * 4.0 / (fullScale - offset); // conversion
  
  Serial.print("Pressure is  ");
  Serial.print(pressure, 1); // one decimal place
  Serial.println("  bar");
  delay(500);
}
10

Hello!

Thank you very much for helping me out today i tested an other sensor...and i figured out the 4 bar sensor is a 3 bar sensor...so it is good but just 3 bar
i figured out with a good 3 bar sensor:
zero pressure is 1,6V
10kpa is ,177V ~0,17V/10kpa pressure
195kpa is 4,65V and this is the sensor limit above that it cant read just shows 4,65 mayne 4,66

So i bought a wrong sensor but the part numbers are correct....
So the sensor is linear i can do the math now i just need to replace a sensor....with a good 4 bar one
i tested a Cummins map sensor too its a 3.5bar sensor so its reads about 2.5bar real time pressure
Im going to get a new sensor and maybe i can do the measurements again with good results :smiley:

Thank you very much for writing!

11

If zero bar is 1.6volt, then the 'offset' value in the sketch from post#8 must be 1.6 / 5 * 1024 = ~328.
That 'fullscale value is calculted for max pressure at 4.5volt, so remains 4.5 / 5 * 1024 = ~922.

So just change offset = 102 to offset = 328,
and change 4.0 to 3.0 in case you're using a 3bar sensor.
Leo..

12

Hello!

I ordered a new sensor i would like to use 4 bar to read 3 bar pressure and 1 bar atmosferic pressure after i need to check the sensor readings from 0 to 3 bar with 0.1 bars so 0 next 0.1 next 0.2 and so on to 3 bar
After i need to figure out what resistance it should read at what celsius...after i need to make a program with lcd screen!
Anyone who helped me thank you very much!
As soon as i can check the sensor readings i will update thus thread!

Thanks Ricsi!

13

Wawa:
With an 'offset' and 'gain' in the maths formula you can display whatever you want,
But you can't do anything about a 'clipping' sensor (sensor can't output more than 5volt).

Know nothing about those sensors, but common pressure sensors are usually rated between 0.5volt and 4.5volt.
Here is the formula that can work with the 'low' value (at 0.5volt), and 'top' value (at 4.5volt).
x.xx is the number to display at 4.5volt, e.g. 4.0 for a 4bar or 400.0 for a 400kPa sensor.

pressure = (rawValue - offset) * x.xx / (fullScale - offset);

You only have to tweak the fixed 'offset' and 'fullscale' A/D values, to calibrate the sensor.
See (untested) example.
Leo..

int rawValue; // A/D readings

int offset = 102; // zero pressure adjust
int fullScale = 922; // max pressure (span) adjust
float pressure; // final pressure

void setup() {
  Serial.begin(9600);
}

void loop() {
  rawValue = analogRead(A0);
  pressure = (rawValue - offset) * 4.0 / (fullScale - offset); // conversion
 
  Serial.print("Pressure is  ");
  Serial.print(pressure, 1); // one decimal place
  Serial.println("  bar");
  delay(500);
}

This code works perfectly on the serial port.But I can't transfer this to Nexion display.Is there anyone who can help?