Low Resistance value measurement

[Leonzio]

Hello,
I'm building a new board in order to measure water pressure using some sensors which would provide a variable resistance depending on the level of pressure of water in a pipe.

Electrically they're not so different from a potentiometer, the problem is that the R value is so low (range from 86 to 330 Ohm) that the classic RCtime schema cannot be applied.
I need at least 8 bit resolution from low to high range.

Could you please suggest me the best schema to connect such sensors to a 16F877A?

Thanks
Leonzio, from Italy

[Charles Linquis]

You could make a voltage divider with another resistor, and then use the A/D converter to measure the voltage at the junction.

[Leonzio]

Thanks for suggesting, but I think this would require too current or would provide a very limited resolution due to the low value of the resistance to measure.

I think I should put some sort of amplifier in the middle, and this is a schema I'm looking for.

Regards
Leo

[Charles Linquis]

Why will it take too much current? if you put a 200 ohm resistor in series with the 330 ohm sensor, the total is 530 ohms, less than 10mA of current at 5V.
Unless you are battery-powered, that shouldn't be too much.

You should be able to get plenty of resolution with this arrangement.