Fotonic™ Sensor and Surface Finish or Smoothness Effects

MTI Instruments has run a series of experimental tests using a standard MTI-1000 Fotonic Sensor looking at various surface finish samples. These tests were conducted by adjusting the MTI-1000 for normal operation against a 2-L surface; and then without changing this adjustment, other surface samples were substituted. 2L is a finely lapped, mirror-like surface. The additional samples were 8L, 16G, 63G, 63P, and 125M. These are considered "standard" surface finish reference numbers used throughout the machine tool industry and represent a wide variation in finishes. These results are significant in that they show a relatively small error in our standard calibration procedure regardless of the extreme variation in surface finish and condition. This accuracy exists up to a No. 63 surface finish with only about a .5 mil equivalent displacement error up to a No. 500 surface. The dynamic error, i.e. slope of calibration curve, is nearly undetectable and is probably less than the experimental error of the tests themselves. When using the Fotonic Sensor to measure smoothness or surface finish, the probe is usually separated from the target (specimen) at a distance which puts the standard Fotonic Sensor curve at its output peak.