Try downloading the free book:
Facilities & Workplace Design: An Illustrated Guide
by Quarterman Lee, Arild Amundsen, William Nelson & Herbert Tuttle
You can find it here: http://www.strategosinc.com/dl0_facdes.htm
You can create a simple accelerometer with a spring of constant (k), a block of mass (m), & a linear potentiometer set to measure displacement in the same axis as the rise and fall of your roller.
For the block, the mass (m) is the weight divided by the acceleration due to gravity (g).
For...
