hey everyone
We are in Prépa in New Caledonia, we have a project to do, our project is to build kind of a pillow for wheelchair in order to decrease the bedsores. The pressure is varied in the cushion and mesured with a pressure sensor (MPX2100AP). Our problem is that the sensor give us too small values (up to 2.8mV) and the arduino card can only read values above 5mV. So we wanted to build our own voltage amplifier, however, we don't know how. We already saw some systems with resistances and transistors but we don't know which one to choose and the exact components needed. So if you have an idea of circuit that can fit to our system or an other solution or any ideas you are more than welcome.
Look into OpAmp circuits. Of course I could just give you a circuit but if you don't understand what's going on there's little hope you can bring your project to completion - do read up on some web tutorials. I bet you'll be able to find them in your own language as well, if you prefer that over English.
The sensor gives an output of up to 40 mV, so you're only using part of the range. I'd go for a total gain of about 1,400 (may need two OpAmps in series), so your 2.8 mV signal becomes just under 4V, giving you a bit of a margin for higher pressures. You may consider a gain of 1,000, giving you 2.8V output on your 2.8mV signal, and a good margin for higher pressures (from heavier patients or so).
Just about any single supply, rail to rail OpAmp will do for this project.