THE TRANSITION FROM STATIC TO DYNAMIC FRICTION
Microprocessor control provides the capability of accurate data logging. This has enabled Ray-Ran to take a different approach to measuring static friction. The force applied to the test sample attached to the sled is measured by a very sensitive load cell. The force is gradually increased and the load cell measurements recorded. At the precise instance that the sled moves, the force measured by the load cell reduces. This reduction is called the hysteresis drop. The microprocessor can be calibrated to respond to a certain amount of hysteresis drop and when this happens, the load cell readings are "back tracked" to the highest previous reading recorded which in fact will represent the static coefficient of friction.
Measurements have been compared with a tilting table instrument and found that the microprocessor controlled instrument provides better results. The main reason for this is that there is still a time delay between the eye observing motion.