Pressure sensor and OpAMP circuit design

[Building_A_Robot_Fish]

Hi,

Can anyone help me with a bit of circuit design please.

I have a differential pressure sensor with a 320mV full scale span and some rail-to-rail OpAMPs (see attached) all from the same 5v source.
I want 0-5v volts presented to one of two A/D pins on a PIC so that I can measure (a) the differential between the two ports of the sensor and (b) the polarity i.e. which port is at the higher pressure.

This may not be the best way to skin this cat (no offence to kat lovers intended) so alternative solutions welcome. Oh, and please be aware that I have very little knowledge of this subject (obviously!) so please keep the help in 'xxxx for Dummies' style.

Thanks
Steve

 

[The Real MicroMan]

Look up a circuit called a differential op-amp amplifier. It will tell you how to pick you resistors to get the right amount of amplification. Then on the positive input of the op-amp put 2.5v on it. This will give a DC offset, you need this because you want polarity. So basicly 2.5 to 5v is one side of the sensor and 2.5 to 0 is the other. that's all you'll need

 

[Building_A_Robot_Fish]

Thanks m8. Puchased an instrumentation amp as I could only find one differential amp and that was SMT. Wired it up and solution worked first time. Cheers

 

[John Sorensen]

You didn't mention what kind of sensor you are using, but I used a bridge like this once (I can't remember the brand but they were later conquered and taken captive by Honeywell), Sensym I think, anyhoo, it wasn't temperature compensated so it made a better thermometer than pressure sensor. I ended up using an external thermistor and corrected for it in software, but since the pressure sensor has a faster response to temperature than the thermistor, it is still sensitive to rapid temperature changes.

fwiw,
j.