Who invented the micrometer first?

The first such measuring tool was patented by French inventor Jean Laurent Palmer in 1848 and was called "threaded caliper with round vernier frame". We still use this typical feature to manufacture outside micrometers. The introduction of the micrometer into the mechanical world began when two American engineers, Joseph R. Brown and Lucian Sharpe, visited the Paris Exhibition in 1867. Their attention was attracted by Palmer's invention and they were very interested. After improving Palmer's design, the product was mass-produced and successfully promoted in the market by these two partners. When the Swiss company TESA decided to make an outside micrometer, they repeated the story that happened in the past and made this product the company's first product. Except for individual cases (such as measuring gear micrometers), the micrometers we use follow the Abbe principle (Abbe principle), just like a comparator. The micrometer mandrel is processed by a modern grinder. The thread profile has a high precision and the pitch deviation is negligible. The processing conditions ensure the extremely low measurement uncertainty of the micrometer.