The least count is an important defining parameter for any kind of scale. It is defined as the minimum value that can be measured on the scale and is the distance between two small graduations. The least count is also significant because it is directly linked with the accuracy of an instrument and in some cases accuracy and least count are used interchangeably although they hold different meanings.
Determining the least count of a vernier caliper is a simple process and it can help make taking readings a quick and sure process using the length formula which we will discuss later. To find the least count of the vernier caliper we first need to find out the least count of the main scale of the caliper. To do this simply count the number of small divisions in between two marked units. Then divide the unit by the number of divisions. E.g 1cm/ 10 divisions = 0.1cm.
The function of the vernier scale is to further break down this reading into smaller values. Thus the smallest value of the vernier scale is the overall least count of the vernier caliper. To find out the least count of the caliper, we need to divide the main scale least count by the number of divisions on the vernier scale. These normally lie between 10 and 20 so if the main scale least count is 1mm then the vernier least count for 10 divisions would be 1/10 = 0.1mm. This means that the caliper can measure a minimum length of 0.1mm. To help you remember here is the formula:
Least Count of Vernier Caliper = Main Scale least count/ number of Vernier scale divisions
Once the least count is known for a caliper, then we can use the following formula to find any length easily:
Length= MSR + (VSR*L.C)
Where MSR = Main Scale Reading
VSR= Vernier Scale Reading
And L.C= Least Count of the Vernier Caliper
This method helps eliminate the doubt which is sometimes created when summing up the main scale and vernier scale readings where people may write the wrong number of decimal places or mix up units but if with the least count and length formula you can be sure about the values.
What is least count
LEAST COUNT – THE SMALLEST DIGIT ON THE MAIN SCALE DIVIDED BY THE TOTAL NUMBER ON THE VERNIER SCALE IS CALLED LEAST COUNT OF VERIER CALIPERS. IT IS DENOTED BY L.C= N/S , N- TOTAL NUMBER OF DIVISION VERNIER SCALE , S- VALUE OF THE SMALLEST DIVISION ON MAIN SCALE.,
The difference between one main scale division and one vernier scale division is called least count.
The smallest division on main scale of a vernier callipers is 1mm and 10 vernier divisions coincide with 9 main scale divisions. When measuring the length of a line, the zero of the vernier scale lies between 10.2cm and 10.3cm and third division of vernier scale coincide with a main scale division. Find M.S.R on left of zero of vernier scale. Find L.C. Find length of line
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Msr is 10.2 clearly.
Least count is 1mm/10divisions:0.1 mm
Length of line:10.2plus 3 (vsr) *0.1: 10.23
THE SMALLEST DIGIT ON THE MAIN SCALE DIVIDED BY THE TOTAL NUMBER ON THE VERNIER SCALE IS CALLED LEAST COUNT OF VERNIER CALIPERS . IT IS DENOTED BY L. C = 1 MM\10 = 0.01 MM . , FORMULA FOR FINDING COUNT = L.C = N/S , N- TOTAL NUMBER OF DIVISIONS ON VERNIER SCALE , S- VALUE OF THE SMALLEST DIVISION ON MAIN SCALE ,
hi, what is the least count on an angular vernier caliper with vernier scale division of 60 minutes of arc and main scale smallest division of 0.5 degrees? (smallest division of vernier scale is 1 minute of arc btw)