How to give the minimum limits of balances?


(suresh babu) #1

How to decide limits of balances like primary or secondary?


(sunil kumar) #2

Minimum weight for any balance decide by its least count multiply by 10


(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.

(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 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


(Sanjay Bhardwaj) #6

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


(sunil kumar) #7

USP <41> official monograph for balance


(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%


(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