Charles Wathen
Involved - Posts
Hi gang,
I've run into a pickle with performing calibrations on some precision Mettler UMX2 micro balances. I have class E2 weights that were recommended by Mettler to calibrate the balance on a regular schedule. We calibrate the balances using the differential method. If you look at the specs for the UMX2 micro balance, it's enough to make your hair stand on end:
Linearity: ±0.004mg
Repeatability: 0.0009mg
Resolution: 0.001mg
Using class E2 weights, my cal ratio is 2.82:1 based on the uncertainties of the weight and resolution of the balance. Going to class E1 is not that much better. What are minimum TAR values that you can accept? I've read that 1.5:1 is OK if you use guardbandding, but in my case, I'm using the entire range of the balance. Thoughts?
I've run into a pickle with performing calibrations on some precision Mettler UMX2 micro balances. I have class E2 weights that were recommended by Mettler to calibrate the balance on a regular schedule. We calibrate the balances using the differential method. If you look at the specs for the UMX2 micro balance, it's enough to make your hair stand on end:
Linearity: ±0.004mg
Repeatability: 0.0009mg
Resolution: 0.001mg
Using class E2 weights, my cal ratio is 2.82:1 based on the uncertainties of the weight and resolution of the balance. Going to class E1 is not that much better. What are minimum TAR values that you can accept? I've read that 1.5:1 is OK if you use guardbandding, but in my case, I'm using the entire range of the balance. Thoughts?