Measuring acceleration in g's I am using adxl335 accelerometer with Arduino uno r3 to measure acceleration due to gravity along x axis. I am using 50 ms delay and printing to serial. 
I have two questions, which are;


Can I measure fractional values, like .8 in acceleration due to gravity?
when I shake the accelerometer up down along x axis, I don't see any variations in 'g'?


I am using analog pins and 3.3V power supply from Arduino to power the sensor.
If you read the datasheet you can quickly find that the output of the device is 300mV per g.  That means:


Read the analog value
Convert it to millivolts
Divide it by 300


The result is the g value.  If you do it using floating point then yes, you get fractions of a g resolution.

For instance:

float mv = analogRead(0) / 1023.0 * 5000.0; 
float g = mv / 300.0;


If the analog channel has 1024 steps, that's 5/1024 = 0.0048828V per step, or 4.8828mV per step.  Divide that by 300 and you get a resolution of 0.01628g

As for not seeing variations in X when you shake up and down, maybe that is because you really want to look at the Z axis, not the X. X is left/right, Y is forward/backward and Z is up/down.  It's all in the datasheet - it makes for good reading, I suggest you take a look.