Reading Automotive sensors

Other Hardware Sensors
1

Hey guys im building a flow bench and would like to use a pair of automotive flow sensors "MAF" sensors.

I want to poll both sensors analog values and record them, But I am having issues with the wiring.

Here is the sensors internal diagram:

[If anyone wants to explain this further that would be appreciated, i understand that its a wheatstone bridge used to measure the variable hot film resistor but it seems there are 2 variable resistors? is this to help trim the output based on the temperature? why would you want two sensors to measure temperature? what is the op-amp on the left doing? and the power transistor?]

Here is the wiring on the sensor. We will be using pins 3,4,5,6.

Pin 6 will need 12v power. I will supply this with a regulated 12v power supply, pin 5 will go to regulated power supply ground

4 is the sensor return to the analog pin.

HERE IS WHERE I GET CONFUSED: What do I do for ground wires? tie all of them together?

Also inside the oem ecu they use pull down resistor on the MAF signal line. Do i need to replicate this for any reason? how would i?

2

Tie all grounds together to chassis ground.

im_the_new_guy:
Also inside the oem ecu they use pull down resistor on the MAF signal line. Do i need to replicate this for any reason? how would i?

What do you mean by "how would you implement a pulldown resistor"?

3

Power_Broker:
Tie all grounds together to chassis ground.

What do you mean by "how would you implement a pulldown resistor"?

So tie all grounds together? I dont understand why there are 2 signal wires? why does there need to be two grounds?

I mean should i just add pull down resistors across the single signal back to ground or something. I tried to do this like a year ago and nothing worked, im about to revisit it and trying to figure out where i messed upu the wiring.

4

I made a rough drawing

IMG_1941.JPG
IMG_1941.JPG2704×2101 815 KB

5

Your drawing looks correct to me.

The reason why you use several sensors (or actuators) for a specific purpose in embedded systems such as cars and planes is for rundundancy. If one sensor goes haywire, you most likely still have more sensors with correct readings.