The sensor is actually 2 copper plates with conductive foam between them acting as a variable resistor with a weight sitting on top. The plate resistance changes as the gravity increases. I don't think the weight size matters too much since the sampling circuit just calculates the time in counts it takes the plate resistor to charge a capacitor. Once the base count is established, the difference in counts between the base count and the new count divided by the base count yields the percent change in gravity. The unit outputs a 12-bit DAC voltage that is centered around 2.5V for zero position, the +/- gravity percent is then added or subtracted to the centered voltage to show the change in gravity. C1 on the board smooths out any ripples, so the signal is pretty clean. I do notice spikes in the signal which I haven't quite figured out why they occur yet, but it has something to do with hot days I've noticed. I need to probably change Labview a bit to smooth out the measurement a little better, but for the most part this kit works pretty well. Having the Arduino board hooked up and talking with Labview is really cool.
Tnx.