How can I evaluate/measure backlash on an optical comparator

[mikea]

There is a debate underway as to how we evaluate/measure backlash on an optical comparator. Currently, with an inspection master, we check for linearity at each inch traversing the table in both directions. The difference of the reading from one direction to the other is reported as backlash. Is this the correct way to measure backlash?

 

[Ryan Wilde]

I am unclear as to whether you are referencing the measurements from the same position or not. Backlash is generally considered the error at the same point when taking ascending and decending readings. The easiest method is to go directly to whatever point you are measuring, document the measurement, and then immediately take a measurement at the same point in the opposite direction, referenced to the same point.

Ryan