Low output pressure transduce Q

I'm looking to buy a pressure transducer that has the output of 0-100mV for full scale. Seeing as this only equals to 31 steps on the ADC (provided a 3.3v system)... is there a way to amp up the output signal to say 330mV or even something higher and still keep a reasonable amount of accuracy (say 1 or 2%, sensor itself is accurate to .25%)?

Thnx.

The easiest solution not requiring external components is to use the internal band-gap voltage (1.1vdc) as the analog reference voltage, then 0-1.1vdc = 0-1023 counts of resolution and your 100mv max signal value will report around 90-100 counts. Still not too great. Better resolution can be had using external op-amp to raise the signal level or use an external ADC chip that has configurable gain settings.

http://arduino.cc/en/Reference/AnalogReference

Lefty

Even the built-in 1.1V reference is subject to a large variation, anywhere from 1.0V-1.2V at room temperature.

I think a precision op-amp amplifier solution with precision resistors would be the way to go in this case, or an instrumentation amplifier that has all that built in.

--
The Rugged Circuits Yellowjacket: 802.11 WiFi module with ATmega328P microcontroller, only 1.6" x 1.2", bootloader

Shoot I just remembered... I have to use 5v ADC... cause I have another operation using 5v. :frowning:

As far as the op amp option... LM358 a good way to go?

As far as the op amp option... LM358 a good way to go?

No, it is not a "precision" op-amp. Its worst-case offset voltage is 7mV, and if you apply a gain of 10 (say) then that's 70mV of offset worst-case (and your signal is still only up to 1V from 100mV). So 70mV of error in a 1V signal is 7%.

You want an op-amp with 1mV or less of offset voltage (and that across the temperature range you plan to work at). Maybe the LM201AN:

--
The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected

What variable in the datasheet is total gain Voltage? Avd?

BTW thanks a lot for the help.

RobDrizzle:
What variable in the datasheet is total gain Voltage?

BTW thanks a lot for the help.

Gain of a op-amp is determined by the ratio of external resistors wired between the input and output terminals of the op-amp, the basic op-amp itself has tremendous gain, too much to be useful or stable for amplification purposes, therefore a negative feedback path is used to set the desired stage gain. Any basic primer on op-amp circuits will show how you calculate the resistor values to set the gain of the circuit.

Lefty

An op-amp has to be configured for gain using some resistors and proper wiring:

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

Lefty I'm reading up on it now... Thanks.

Any thoughts on this... lol... I can't win now and days. Thanks