Dear All.
I am new in the PIC project and currently working with a project that requires to measure battery voltagr from 10 to 18 volts.As i have read nearly all the post in this forum i have notice that the only way to read voltages into a PIC is to limit the voltage between 0 to 5 volts.

Many have recomended to use resistors but is there any way to get muct better reading as resistors will change when it is subjected to heat.

Basically i want to read the voltages of a car battery and also the fuel indicator and change all of this to a digital read out.One way i found out via the internet is to use OBD (Onboard dignostic) codes where we could use the PIC16F84 to conver the manufactures code to display the values comming out of the car ECU (Electronic Control Unit) on all injectors car before 1996.

Has anyone done such a project before that can give me a helping hand on a better way to read voltages using at least an op-amp or an isocoupler.Or has anyone built a OBD system before?

Thank you