The smallest amount that can be measured by any instrument is called the least count of that instrument. For example, suppose the scale that draws the line draws a line to measure a smaller amount of 0.1 cm and we cannot measure an amount smaller than that, so as per the definition of least count, the least count of our scale is 0.1 cm.
It is difficult to measure small distances with a simple scale, so to measure small distances, a French scientist Pierre Vernier created a scale called Vernier calipers.
A sliding scale is attached to the main scale in the vernier calipers scale, with the help of the vernier calipers scale, the internal and external distance of any object can be measured without any error. That is, there is very little error in the distance measured with this scale. The least count of any Vernier caliper scale is 0.10 mm. Which is much less than the normal scale.
The following distances can be easily measured with the help of Vernier calipers –
External distance: such as the length of an object, etc.
Internal distance : like diameter of a sphere
Depth: Such as the height of a hole, etc.
Working
There are two scales in the Vernier calipers scale, both of which are read properly and the final value is obtained.
First Scale: Man Scale (Main Scale) – Its value is the one that is first obtained from zero.
Second scale: Vernier scale – The value where the lines of both the scales overlap each other.
For example, on the measurement of an object, we get the following value on the scale.
To read the main scale, write the value before zero, as here 2.1 is visible before 0, so 2.1 is the value of the main scale.
In vernier scale the line of both the scales should come on each other, we read this value on vernier scale, both the line is coming up on 3 i.e. superimposed on each other.
The least count of the main scale is 0.1 cm and that of the Vernier scale is 0.01.
So the value we get is as follows –
Main scale : 2.1 cm
Vernier Scale : 0.03 cm
Thus, the net measurement of the object : 2.1 + 0.03 = 2.13 cm
Screw gauge
Scruggs are also similar to vernier calipers, they are used to measure even smaller objects, such as the diameter of a wire, etc.
Scrooge also has two scales –
The first scale is called the principal scale.
The second scale K = rotates, it is called the Vernier scale.
Working
Measurement is done with the help of screw gauge as follows –
Suppose we are finding the diameter of a wire and we get the following values on the scale –
If we look at the main scale on the first measurement, we are getting 5 and on the scale below it, one line is visible more, so in the first measurement, we have got 5 mm and one line more, hence 0.5 mm, so the first measurement It is getting 5.5 mm in total.
In the second measurement, we look at the Vernier calipers scale where we see a match on the main line on the 28th line, so the measurement of the Vernier scale is getting 0.28 mm .
Thus, total measurement = 5 + 0.5 + 0.28 = 5.78 mm
Least count of screw gauge = 0.01 mm.
The screw gauge scale is also called screw gauge.
Least count of screw gauge = bangle gap / total number of parts on the circular scale
