What Are Outer Diameter Measuring Instruments?
Displacement sensors, which are instruments for measuring displacement (change in the position of an object), include non-contact methods, and displacement gauges that use light silhouettes for measurement are often used for dimensional and outer diameter measuring applications, and are therefore called dimensional measuring instruments, or outer diameter measuring instruments.
Many outer diameter measuring instruments use a semiconductor laser (green LED beam), which is compact and non-contact, and can measure with high accuracy without affecting the object to be measured.
Uses of Outer Diameter Measuring Instruments
Outer diameter measuring instruments are used by manufacturers in the steel and metal industry and textile material manufacturers to inspect the appearance of materials and identify different materials in the product development and manufacturing process.
Specifically, they continuously measure the outside diameters of materials to be inspected and identified in real time and with high non-contact accuracy at mass production sites and inspection rooms.
Some outer diameter measuring instruments can be used for both automatic inspection (in-line inspection, where the visual inspection process is incorporated into the line production system) and manual inspection (off-line inspection, where measurement is performed in a separate process from the line).
Principle of Outer Diameter Measuring Instruments
In an outer diameter measuring instrument, a semiconductor laser (green LED light) is emitted in parallel from the light projector. When an object passes through a certain measuring range, the object blocks some of the light and a silhouette is obtained.
By specifying a measurement point on the silhouette, the measured value at an arbitrary point is obtained.
The silhouette measurement is captured by an image sensor in the light-receiving section.
The image sensor may use a device called a CMOS (complementary metal oxide semiconductor), which is an imaging device used in digital cameras.
The light and dark edges are detected from this silhouette and the O.D. dimension is measured.
In the measurement principle described above, the measurement method is called the transmission type, which is not affected by illumination or the surface condition of the object, and outer diameter measuring instruments take advantage of this advantage to achieve highly accurate measurements.
As explained in the overview, the outer diameter measuring instrument is a type of displacement sensor that uses laser light for non-contact and stable measurement, so it can simultaneously measure the gap dimension and the amount of movement (the amount by which an object moves from one position to another).