Measurement System Types and Characteristics

Roughness Meters

Overview

Roughness meters, also called "surface roughness meters," are instruments that measure the smoothness (degree of roughness) of the surface of a target. The main types of meters use either probes or lasers. Conventionally, the most common models used a diamond probe, but optical types have become more common due to concerns of the diamond probe damaging the surface of semiconductors and similar objects during measurement. Some models can measure both flat and curved surfaces. Recently, models that can display a 3D image of the shape based on the data measured from the surface have also appeared.
Examples of applications of roughness meters include checking for wear on metal surfaces, checking cut surfaces, and checking painting finishes. With more and more electronic components being made using thin film processing, some roughness meters can even perform measurement in the order of nanometers.

Construction and Applications

Construction and Applications of Roughness Meters
A
Vertical stand
B
Drive unit
C
Stylus (detector)
D
Table
  • Probes commonly use a tip with a radius of 2 μm. However, for precision-machined products, probes with a tip in the 0.1 to 0.5 μm range are also common. Variations in measured values may occur depending on the probe used, so checking in advance whether the tip is appropriate is essential.

How to Use a Roughness Meter

  1. With a contact-type roughness meter, surface roughness is measured by tracing the probe across the surface of the target. In contrast, a laser-based non-contact roughness meter emits a laser beam onto the target and detects the reflected light to measure the roughness.
  2. The direction of measurement is the key to successful measurement. For example, a processed metal product is generally measured perpendicularly to the processing direction so that the roughness meter can capture the surface characteristics more reliably.
  3. Measurement speed is also a key element for accurate measurement. Measurement is first performed slowly, and the speed is increased until no fluctuation occur in the measured values.

Handling Precautions

  • Periodic calibration is required to perform correct measurements.

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