Profile Meter

an instrument for measuring the irregularities of a surface; the readout of the measurement results is a scale giving one of the parameters used to evaluate these irregularities—surface roughness. The first profile meters appeared at almost the same time as profilographs.

In profile meters, a signal is received from a sensor with a diamond stylus that moves perpendicularly to the surface being measured. After electronic amplification, the signal is integrated to give an averaged parameter, which quantitatively characterizes the surface irregularities over a given length. The most common profile meters have a fixed integration run equal to the length of the sensing trace and read out on a scale after the trace is completed. Some profile meters have a variable integration run that is less than the length of the sensing trace and read out as the stylus moves over the surface. The error in readings varies from ± 10 to ± 25 percent.

The conversion of oscillations from the diamond stylus into voltages may be achieved by several methods. In the USSR, profile meters with mechanotron converters are produced by the Kalibr Factory; they read out an arithmetic average deviation of the surface profile (R_a) within limits of 0.025 to 5 microns and with an error of ± 16 percent for an integration run of 3.2 mm. This instrument may be used to measure inner surfaces with diameters of 6 mm or greater.

Further improvements in profile meters will involve expansion of the number of averaged vertical and horizontal readings and the fitting of devices that analyze harmonic components to form a curve characteristic of the surface irregularities.