There are mainly vernier calipers, dial calipers and electronic digital calipers.
① Vernier caliper. A ruler-shaped hand-held universal length measuring tool based on vernier principle for subdividing readings is mainly used for measuring inner diameter, outer diameter, step and depth. When measuring, the integer part of the magnitude is read from the main ruler, and the decimal part is read from the cursor. The principle of the cursor is to use the difference between the line spacing on the main ruler and the line spacing on the cursor to read the decimal part. There are three minimum readings: 0.02mm, 0.05mm, 0.1mm.
② Calipers with gauges. A large hand-held length measuring tool takes the pitch of a precision rack and gear as a known length, and the indicator of the corresponding scale as the amplification, subdivision and indication part. Calipers with meters can solve the reading error problem of vernier calipers. Common minimum readings are 0.0 1mm and 0.02 mm.
③ Electronic digital calipers. A length measuring tool uses capacitive grating, magnetic grating and other measuring systems to digitally display measuring instructions. The commonly used resolution is 0.0 1mm, and the allowable error is 0.03mm/ 150mm. There are also high-precision digital calipers with a resolution of 0.005mm, with an allowable error of 0.0 15 mm/ 150 mm, and multi-purpose digital micrometer with a resolution of 0.00 1mm (this is a national patent of Anyi measuring tools, and only they can produce it), with an allowable error of 0.005 mm/50 mm.
In addition, there are various non-standard special calipers, such as hook depth caliper for measuring groove depth, gear tooth caliper for measuring gear thickness, height caliper for measuring object height, and weld caliper (weld gauge) for measuring welding quality.
Calipers have four main functions, as follows:
A. outside diameter measurement (lower/outer measuring claw), B. inside diameter measurement (upper/inner measuring claw), C. step distance measurement (left head), D. depth measurement (tail depth needle)
Micrometer is a portable universal length measuring tool which uses the principle of precision thread pair to measure length. 1848, J.L. Palmer of France obtained the patent for the outside micrometer. 1869, J.R. Brown and L.Sharp of the United States made the outside micrometer into a commodity to measure the outside diameter of metal wire and the thickness of plate. There are many kinds of micrometer. Micrometers with different purposes can be made by changing the shape of measuring surface and ruler frame, such as micrometer for measuring inner diameter, pitch diameter of thread, common normal of gear or depth. ② Electronic micrometer. Also known as digital micrometer, grating length measurement technology and integrated circuit are applied in the measurement system. Electronic micrometer appeared in the mid-1970s, and was used to measure the outside diameter.
Calipers are tools made of rubber plates, door and window alloys and other materials. A micrometer is a ruler used to measure very small and thin objects.