A profilometer is a device used to measure the roughness of a surface. There are two classes of profilometers: contact and non-contact. Most of these devices measure the vertical difference between the high and low point of a surface in nanometers. This tight measurement readily illustrates the difference in objects that look or feel the same without direct measurement. While a profilometer is common in many fields, one of their main uses is measuring the roughness of road surfaces.
A contact profilometer uses technology much like that of a record player. A stylus with a diamond tip is run over a sample of a material. The stylus records the groves as a wave pattern and sends the information back to a computer. This computer can use the wave to directly model the surface as the stylus moves. By the time the process is done, the system will have an accurate model of every location measured.
These were the first types of profilometers and are still very common. They have many advantages over non-contact tools, but are limited to use on samples. They are generally difficult to use in the field since the surface being examined needs to fit under the reading needle.
A non-contact profilometer uses beams of light to read a surface. Much like the common range finder, they shoot a beam out and measure the time it takes to return. This gives two major advantages to this style of profilometer over the contact version. First, it easily works in the field, as it can just sit on a surface and it suffers almost no wear since none of its parts touch anything.
This profilometer style has one major disadvantage. Since it sends data to the central system using digital code, the surface modeling for the area needs to be translated into human-usable data. This requires an additional step that the contact version doesn’t need, and it can greatly increase the modeling time.
One area where profilometers are very common is in measuring a road's roughness. When used for this purpose, the profilometer, along with several other measurement tools, connects to a moving test system. These systems can be anything from a standard car to a specialized dolly that just moves the tools. Since these profilometers are used in the field over a distance, they are always non-contact devices.
The goal of these road tests is to find the roughness of a stretch of road. The results will help determine if a road needs repair or resurfacing. It also helps when determining information for tires and drive systems, ensuring that a car provides maximum power and grip in a variety of road conditions.