I am interfacing an ambient air pressure sensor to a PIC ADC. The sensor outputs a voltage between 0v and 5v, however I am only interested in reading output voltages between 3.5v and 4.5v and would like to get the maximum ADC resolution in that range.
The best I can figure out is that the PIC ADC will read voltages between Vss (0v) and Vdd (+5v) or Vref (0v - 5v). I am able to set the upper limit of the range with Vref, but I have no idea how to set the lower limit.
Can I somehow shift the output voltage of the sensor (subtract 3.5v) or is there a way to set the PIC to use 3.5v as the lower limit? The best I can determine from the PIC documentation, it only uses the Vss pin (0v) for the lower limit of the ADC.
Thanks for any help.
The best I can figure out is that the PIC ADC will read voltages between Vss (0v) and Vdd (+5v) or Vref (0v - 5v). I am able to set the upper limit of the range with Vref, but I have no idea how to set the lower limit.
Can I somehow shift the output voltage of the sensor (subtract 3.5v) or is there a way to set the PIC to use 3.5v as the lower limit? The best I can determine from the PIC documentation, it only uses the Vss pin (0v) for the lower limit of the ADC.
Thanks for any help.