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balances - Coggle Diagram

- - - - sensitivity/linearity/eccentricity/repeatability
        
        systematic deviations - limit accuracy
        
        acc criteria is accuracy tolerance/2 = 0.1%/2 = 0.05%
        
        2+ weights used in tests? avoid or error summed tocheck compliance to uncertainty ratio (3:1 in USP)
        
        repeatability/eccentricity = same calib weight used through out test
  - - - for accurate balances K=2 tolerance 0.1% => 2000 x SD or 0.41d (rounding error)
  - - - req for containers
- - - - depending on weighing technology the contribution from each parameter (eccentricity, nonlinearity ect) may change
  - - - environment factors change performance => impact Mmin => safety factor (avg 2?)
      - not need check actual Mmin as repeatabilityerror is pretty much independent of sample mass when get ot few % of capacity
        
        for large scale/precision balances other ba parameters (SE/NL/EC) may be significant at lower end of capacity, must determine the total uncertainty work out Mmin cant just use repeatability)
  - - - due to contributions to uncertainty => check repeatability + sensitivity most frequent (eccentricity/NL by contractors)
    - - 100% capacity weight (or 1/3or capacity if large balance)
        
        NMT 5% capacity calib weight
        
        sensitivity = MPE 1/3 of tolerance (periodically calibrated)
        https://www.dropbox.com/home/QP%20Modules%20(1)/Modules/5%20QC%26Analysis%20100%25%20read?preview=why+use+large+weight+when+checking+sensitivity+error+of+balance.PNG
        eccentricity.repeatability = weight same throughout test, repeatability use weight few percent of capacity this where repeatability error is largest, use tare vessel as this will increase repeatability error thru interaction with environ (air currents etc) this is worst case. Eccentricity use large weight as this is where eccentricity contributes most to error.
        microbalance = higher class cal weights needed smooth wont accumulate contam change mass
        
        low resolution balance ignore the above as major uncertainty contibrution is from readability( roundin error) so use cal weight near bal capacity
        
        tare vessel mayinteract with environment => repeatability error
    - - still check the value they give to calib weight
      - can reduce risk => less frequent external weight PVs
- - - - 10 weighings of test weight
        
        SD/smallest net weight user plans to use
        
        value =< 0.1%
        
        passes this is the smallest net weight measure and pass repeatability.
        
        mmin = k × s/required weighing tolerance K coverage
        K=2 and tolerance = 0.1% for "accruate" simplifies to
        Mmin = 2000xSD or 2000x0.41d (accotun rounding error) which ever highest.
        
        internal safety factor (account environmental variables that'll change Mmin
    - - 0.1% of test weight
        
        calib std uncertainy =< 1/3 of calib tolerance (uncertainty rule ~ 4:1)