Although the scriber and caliper appeared long ago, the vernier caliper with modern measurement significance is the Frenchman Jonyer? Pi was invented in 163 1. He described the structure and principle of Vernier caliper in his mathematical book "The Structure, Use and Characteristics of the New Quadrant Circle", and his name Vernier also evolved into the English word vernier, which is still in use today.
The vernier caliper has a simple structure, which is a ruler and a sliding vernier. The scale line of the main ruler is one millimeter, while the cursor has scales of 10, 20, 50. Take the division of 10 as an example, call it a ten-degree vernier caliper, and so on.
The total scribing length of 10 indexing vernier is 9 mm, and the measuring accuracy can reach 0.1mm; The length of 20-index vernier is19mm, and the measuring accuracy can reach 0.05mm; the length of 50-index vernier is 49mm, and the measuring accuracy can reach 0.02mm.. ..
As we all know, one millimeter is very small. Due to the limitation of scale line, visual measurement can be accurate to 0.5 mm at most. Vernier caliper can be accurate to 0.02 mm, because it has one more vernier than ordinary ruler.
The main difference between the cursor and the ruler is that the unit length of the scale line is different. The unit length of each grid on the main ruler is one millimeter, and the unit length of each grid of the cursor depends on the scale value, in which the unit length of each grid of the 10 scale cursor is 0.9mm, the unit length of the 20 scale cursor is 0.95mm, and the unit length of the 50 scale cursor is 0.98mm, which is 0.65438 different from the unit scale of the main ruler respectively.
At this point, you may have understood that the difference of this unit scale is their minimum measurement accuracy. Through the accumulation of the unit scale difference between the main ruler and the cursor, the tiny length difference that could not be marked by the scale line was amplified by this cursor and became a numerical value that people could intuitively read.
This method is called amplification method, which mainly includes optical amplification method, deformation amplification method and cumulative amplification method. It is a very common means in the process of research or observation. Screw micrometer (micrometer) also adopts this method.
Take 10 vernier caliper as an example. When the equivalent claws are together, the main ruler is aligned with the zero scale line of the cursor, and their 1 scale lines (excluding the zero scale line) differ by 0. 1mm, the second scale line by 0.2mm, the first scale line by 10/mm and the first scale line by 1mm. If the zero tick mark of the cursor is aligned with the x tick mark of the main ruler, the 10 tick mark on the cursor will be aligned with the X+9 tick mark of the main ruler.
When reading vernier calipers (in millimeters), always read the distance between the zero scale line of the vernier and the zero scale line of the main scale first, take the integer part, and then see which scale of the vernier is aligned with the main scale, and you can get the decimal part of the measurement result. Under normal circumstances, the scale lines of the main ruler and the vernier caliper are not misaligned, so the vernier caliper is generally not evaluated.
When measuring the size of an object, if the thickness of the object is 10.4 mm, the cursor will move to the right and slide10.4 mm. At this time, the zero scale line of the cursor is located between the scale lines of the main ruler10 ~1mm, and the fourth scale line on the cursor will be the same as that on the main ruler. If the nth scale line of the cursor is aligned with the main scale, the thickness of the object is 10+n 0. 1 mm. If measured with a 20-minute vernier caliper and a 50-minute vernier caliper, the thickness of the object is 10+N0.05mm and 10+N0.02mm respectively. Do you know what scale these two N's are?
In addition to vernier caliper, there are dial caliper and electronic digital display caliper. The micrometer principle of dial caliper is similar to that of spiral micrometer, which turns straight lines into curves.