# Sensitivity Requirement Calculation Formula

The sensitivity requirement (SR) of a balance represents the absolute error in using that balance. It can also be defined as the cutoff weight below which a balance cannot measure accurately.

In other words, SR is defined as the minimum weight that causes the pointer of a balance to move by one division.

As per USP, sensitivity requirement (SR) is the maximum change in load that will cause a specified change, such as a particular quantity of pointer scale division marks, of the pointer or indicating component of the balance.

#### Sensitivity Requirement (SR) Formula

SR = Weight / no. of division moved

Example:

Calculate the SR of a prescription balance if a 30 mg weight on this balance was able to move the pointer by 2 divisions.

30 mg/2 divisions =x/1

x = 15

So, SR = 15 (This is not satisfy Class A prescription requirement).

Note: The sensitivity requirement for an electronic balance is supplied by the manufacturer and the class A prescription balance must have a sensitivity requirement (SR) of 6 mg or less.