Electrical – How to reverse a pressure transducer output voltage


I am trying to set up an air compressor on my truck and run it through a Ford APCM (auxiliary power train control module). It has a 5v output. The APCM has a custom throttle control input on it. It will run the truck at 1200 rpm at .5v input and 2500 rpm at 4.5v

I have a 150psi 0-5v pressure transducer for the air tank pressure. The pressure transducer outputs .5v at 0 psi and 4.5v at 150 psi.

I would like the truck to run at 1200 rpm (.5v APCM input) when the air pressure is at 150 psi (4.5v transducer out put) and run at 2500 rpm (4.5v APCM input) when the system is at 0 psi (.5v transducer output).

I have messed around with and op amp circuit and I have got it close on both ends but can't get my desired voltages at both ends. Is an op amp correct for this or is there a better way to do what I am trying to do?

Best Answer

Use a diff-amp circuit to subtract the sensor output from your high idle reference.


simulate this circuit – Schematic created using CircuitLab

I also added a buffer to the sensor input to give you a high impedance input.

It would be prudent to add some noise filtering in there though and probably voltage limiting to the output.

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