Hi Hemil
I'm starting out on making a differential air pressure measuring circuit
I'm assuming that you plan to use two of the MPX4115A sensors, take a reading from each and then calculate the pressure difference between them?
Looking at Figure 4 in the datasheet, the straight line portion of the output of the sensor seems to be between 15 kPa and 115 kPa. I'm assuming that this range is OK for you - but you want to measure the difference between two sensors where the difference is in the 0 to 1 kPa range?
Page 2 of the datasheet gives the sensor sensitivity as roughly 45mV change in output per 1 kPa change in pressure. With the standard (nominal) 5V reference to the Arduino ADC, I think that works out at (0.045 / 5) * 1024 = about 9 increase in output value per 1 kPa.
I was wondering if this sensitivity can be reduced as much as possible.
Do you mean increase the sensitivity, i.e. make the Arduino able to read smaller changes in differential pressure with more precision?
Two ideas come to mind. If you look in the reference section of this website about the analogue pins and "analogRead()" function, there is information about setting different reference voltages for the ADC. If you can apply a clean and stable reference voltage lower than the default 5V supply, you will get a bigger value output per mV of input.
Another approach would be to add an external differential amplifier between the sensors and the Arduino, so it compares the sensor outputs and generates a difference voltage, with the gain of the amplifier set to make best use of the Arduino input range.
Regards
Ray