How Does a Thermocouple Interface with an ECU to Control Fuel Injection?

[meestahbig]

Hi everyone, please let me know if this posting belongs elsewhere.

I have a car that runs a motronic 2.7 fuel injection system and with that there is a thermocouple probe in the exhaust pipe (standard K-type thermocouple). This thermocouple goes into a black box which then sends out a signal to the fuel injection ECU telling the system how how the exhaust is.

And actually it seems its much simpler than that. It does not tell the fule injection ECU the temperature, what it does is it sends 0v if the temp is 920 degrees and sends 13v if the temp is above 980. I'm not sure what signal it sends if the temp is below 920, maye its 5v.

does anyon know how this would work. could I just the AD595 chip. but how would I get the binary state of 0v or 13v?

any ideas. thx, Big

 

[meestahbig]

Here is a little more detail about what I am trying to achieve...

the input is the K-type thermocouple.

This is what I need the circuit to do:

At 980 celsius (+/- 20 degrees), I need it to send 13vdc output. under 980 degrees, the output on this should be 0vdc.

Also, there is another circuit v out that illuminates a small dash panel bulb. above 900 (+/- 20), the bulb should flash. above 940 (+/- 20) the bulb should stay on permanantly.

that's it! LOL.