Does anyone what signal a typical aftermarket Temp sender and Pressure sender would output to the gauge ?

 

Is it a linear voltage representation of the temperature/pressure sensed?

Most signals that are generated will be as close to linear as possible as they are used for instrumentation . Only a few digital sender units will fluctuate the signal for a processor to sort and sent to the read out/display.

You also need to remember that a temp sender is just a resistor that varies its resistance with temperature, a pressure sensor can be either the same OR have a 5v feed and give a 0-5v output on the sensor wire....

So I could set one up for datalogging if I can work out a min and max and there corresponding output voltage ?

 

eg. temp sender....if I measure the voltage at a known min and high tempertaute (0 and 120degrees for example) then I can set that up for datalogging and it can measure the full scale inbetween accuratly ?

Yeah the temp is easy because you can measure it against a decent temp guage and see the corresponding values. Pressure is more difficult to calibrate but is certainly possible. If you can supply the temp sensor with a constant current, the voltage will then be directly proportional to the resistance :)

Cool, Cheers :D