How to decide limits of balances like primary or secondary?

# How to give the minimum limits of balances?

**SajayBhardwaj**(Sanjay Bhardwaj) #3

Minimum weight of balance

```
When
Minimum operating range shall be calculated, it should be in such
a way that, the tolerance should be same or higher than the least
count.
For
Example: For 120.0 g Balance capacity if least count is 0.001g /
1.0 mg. Then Minimum operating range is 200.0 mg, considering
tolerance limit ±
0.5%.
Note:-Minimum
operating Limit is 200 times of least count of balance.
```

**SajayBhardwaj**(Sanjay Bhardwaj) #4

For Maximum

```
Maximum
weight of operating range shall be calculated based 80% of
balance capacity as per annexure 1.
For
Example : for 120 gm Balance capacity maximum capacity shall be
calculated 80% of balance capacity. Then maximum capacity 96
gm,considering tolerance limit ± 0.5%.
```

**sunil**(sunil kumar) #5

Yes sir operating range should be 80% of its maximum capacity but minimum capacity in not necessary 200 time of least count it should be 50 to 100 time . Which may be determine by standard deviation of repeatiability

**SajayBhardwaj**(Sanjay Bhardwaj) #6

How can be define 50 or 100 time of least count please give reference of guideline

**Awad**(Dr. Ahmed Mohamed Awad) #8

USP General chapter 1251

Mettler Toledo GWP (Good weighing practice)

EURAMET Calibration Guide No. 18 , Version 4.0 (10/2015)

Regarding the max it is equal to the capacity as mentioned by Sartorius mechatronics document, not 80%

**Awad**(Dr. Ahmed Mohamed Awad) #9

A simple formula for calculating minimum weight is described in USP 1251 for analytical balances

minimum weight = 2 X Standard Deviation obtained from balance calibration / weighing tolerance budget