Digital Barometer using PIC Microcontroller and MPX4115A Pressure Sensor – XC8

Digital Barometer schematic (1)

The Motorola MPX4115A is an atmospheric pressure sensor powered by 5V and delivers and output from ~0.25V to ~4.75V based on the pressure detected at room temperature (25°C). The device provides a linear output based on pressure. As the pressure rises, the output voltage of the sensor rises as well with ~0.25V represents <15 kPa pressure relative to a vacuum and ~4.75V represents >115 kPa.
Note that  1 atmosphere of pressure at sea level is equal to 101,325 Pa or 101 kPa. The graph below shows a typical output response of an MPX4115A pressure sensor, below 15KPa and above 115KPa the voltage doesn’t change.The MPX4115A is thus an ideal sensor for microcontroller based barometer or altimeter applications.

Digital Barometer


  • 1.5% Maximum Error over 0° to 85°C
  • Ideally suited for Microprocessor or Microcontroller– Based Systems
  • Temperature Compensated from –40° to +125°C
  • Durable Epoxy Unibody Element or Thermoplastic (PPS) Surface Mount Package

Application Examples

  • Aviation Altimeters
  • Industrial Controls
  • Engine Control
  • Weather Stations and Weather Reporting Devices

Digital Barometer schematic (1)

 Circuit diagram
As shown on the circuit diagram above, it is very easy to interface the MPX4115A to a PIC, if you are using the 8-pin sensor, connect pin 2 to +5V, pin 3 to ground and the output is on pin 4 (connect to analog pin of PIC). leave the rest unconnected. If you are using the 6-pin sensor, pin 1 is the output (connect to analog pin of PIC), pin 2 to ground and pin 3 to +5V. Leave the rest unconnected.
Note: Pin 1 is noted by the notch in the lead



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