Tolerance when verifying an analytical balance

Dongzkie

Involved In Discussions
#1
Hello Sir, please if you could help. Need to know the tolerance when verifying analytical balance. Does the readability means the tolerance?
 
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dwperron

Trusted Information Resource
#2
Analytical balances typically have several "tolerances" that need to be addressed when you calibrate one.
Here is a sample specification set:
1558532063753.png

Readability is the resolution of the balance. This is not a tolerance.
Repeatability is derived by making a series of measurements of the same mass at the same location on the pan.
Linearity is performed by using test weights from the minimum reading to the balance capacity.

Most analytical balances also have a tolerance for off center balance:
1558532502016.png
Here you would take a test weight, measure it at the center of the pan, and then measure the same weight at the edge of the pan in all four quadrants.

Some labs combine all of the tolerances into an "accuracy" specification, but this is extremely poor practice.
 

Dongzkie

Involved In Discussions
#3
assuming that I have balance that has capacity of 220g and has a readability of 0.0001g and using a class F test weights what would be my tolerance for my balance is it as per the tolerance of the class F test weights?

thanks

Analytical balances typically have several "tolerances" that need to be addressed when you calibrate one.
Here is a sample specification set:
View attachment 25733

Readability is the resolution of the balance. This is not a tolerance.
Repeatability is derived by making a series of measurements of the same mass at the same location on the pan.
Linearity is performed by using test weights from the minimum reading to the balance capacity.

Most analytical balances also have a tolerance for off center balance:
View attachment 25734
Here you would take a test weight, measure it at the center of the pan, and then measure the same weight at the edge of the pan in all four quadrants.

Some labs combine all of the tolerances into an "accuracy" specification, but this is extremely poor practice.
 

dwperron

Trusted Information Resource
#4
All you have given me is the capacity of your balance and its readability. Neither of those is a tolerance.
You need to provide the linearity, repeatability, and off axis specifications in order to know the tolerance of your balance.

If you are to state that you are using the readability of the balance as your accuracy tolerance then using Class F weights are not anywhere near accurate enough. A 200 g Class F weight has a tolerance of 0.040 g, your readability is 0.0001 g.
 
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