What is the difference between your accelerometers?

The Low-g Accelerometer has a +/- 5 g range and is by far the most popular. If you will be doing basic classroom experiments (carts colliding, students jumping, etc.), this is definitely the recommended sensor.

The 3-Axis Accelerometer is really just 3 of the Low-g Accelerometers in the same housing. It has 3 sensors mounted orthogonally so that you can use it in more complicated motions such as roller coaster rides. Just calculate the square root of the sum of the squares of the 3 sensors, and you get the magnitude of the resultant acceleration. The only drawback to this model is that it costs more than the Low-g Accelerometer.

The 25-g Accelerometer was our first model accelerometer. The range is +/- 25 g, which we now only recommend if you are doing fast collisions and need to see quickly changing accelerations of a large magnitude.

Note that if you are considering the 3-Axis Accelerometer, you might also want to consider using the Wireless Dynamics Sensor System, order code WDSS, $249 which includes a wireless 3-Axis Accelerometer as well as a force sensor and altimeter.