Weighing error

Provided that the balance is functioning correctly, the main source of error is in the weights themselves these should be calibrated by one of the standard methods so that their relative values are known, and they should be carefully cleaned with tissue paper and checked from time to time. To make the best use of the balance, weighing should be carried out by the method of swings, but for this purpose it is necessary first to determine the sensitivity of the balance. 

A second example is also informative. When samples are obtained from a normally distributed population, their values must be random. If results for several samples show a regular pattern or trend, then the samples cannot be normally distributed. This may reflect the fact that the underlying population is not normally distributed, or it may indicate the presence of a time-dependent determinate error. For example, if we randomly select 20 pennies and find that the mass of each penny exceeds that of the preceding penny, we might suspect that the balance on which the pennies are being weighed is drifting out of calibration. 

Each of these last forms weigh the errors in various data points differently, so some may be more suitable than others, depending on the precision of the data. Ideally all should yield the same values of the reactivity ratios. 

Equation (8-66) contains two types of design parameters that can also be used for tuning purposes. The move suppression factor 8 penalizes large control moves, while the weighting factors Wj allow the predicted errors to be weighed differently at each time step, if desired. 

Care should be taken to avoid powerbil suction or air flow on the mixer or the weigh hopper from which the ingredients feed into the mixer. If the dust-collection suction on the mixer is too strong, vital ingredients may be sucked out. If the dust-collec tion suction on the weighing system is too strong, errors in weighing may result. 

Overfill drum due Calibrate weighing devices and maintain equip-to operator error ment in good working order or valve failure,. metering pumps can lead to opera- tor exposure, slip- fill operation with weighing device pery floors, spread of flammable liquids. CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29... 

Analysen-. analytical, -befund, m. analytical finding or result, -bericht, m. report of analyses, analytical report. einwa(a)ge, /. weighed portion for analysis. fehler, m. analytical error. 

Whatever cleaning method is used, the possibility of removal of solid metal is present. This will result in error in the determination of the corrosion rate. One or more cleaned and weighed specimens should be recleaned by the same method and reweighed. Loss due to this second treatment may be used as a correction to that indicated by the first weighing. 

Calibration of apparatus and application of corrections. All instruments (weights, flasks, burettes, pipettes, etc.) should be calibrated, and the appropriate corrections applied to the original measurements. In some cases where an error cannot be eliminated, it is possible to apply a correction for the effect that it produces thus an impurity in a weighed precipitate may be determined and its weight deducted. 

It should have a high relative molecular mass so that the weighing errors may be negligible. (The precision in weighing is ordinarily 0.1-0.2mg for an accuracy of 1 part in 1000, it is necessary to employ samples weighing at least about 0.2 g.)... 

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