Detection of gross errors

By automation one can remove the variation of the analysis time or shorten the analysis time. Although the variation of the analysis time causes half of the delay, a reduction of the analysis time is more important. This is also true if, by reducing the analysis time, the utilization factor would remain the same (and thus q) because more samples are submitted. Since p = AT / lAT, any measure to shorten the analysis time will have a quadratic effect on the absolute delay (because vv = AT / (LAT - AT)). As a consequence the benefit of duplicate analyses (detection of gross errors) and frequent recalibration should be balanced against the negative effect on the delay. 

To illustrate the usage of test functions for the detection of gross errors, we will consider the problem presented by Ripps (1965), which has been presented in Example 5.1. The residua in the balances and their corresponding variances are given by... 

Iordache, C., Mah, R., and Tamhane, A. (1985). Performance studies of the measurement test for detection of gross errors in process data. AIChE J. 31, 1187-1201. 

Tong, H., and Crowe, C. M. (1995). Detection of gross errors in data reconciliation by principal component analysis. AIChE J. 41, 1712-1722. 

Serth, R. W., Valero, C. M., Heenan, W. A., 1987. Detection of gross errors in nonlinearly constrained data a case study. Chem. Eng. Commun. 51, 89. 

Crowe, C.M. (1989), Test of maximum power for detection of gross errors in process constraints, AIChE J. 35, 869-872... 

After the reconcilation is effected, adjusted values are substituted into equations of the horizontal band 1, and the unmeasured values (vertical band 1) are simply computed. In a similar way, also a complex processing of the measured data (propagation of random errors, detection of gross errors, etc.) can be realized see again Chapter 9, or for example Madron (1992). Measured data inconsistency is analyzed using the equations from bands 3 and 4a only. The remaining equations contain no information in this respect. 

Fill BOD bottles with the sample in subdued light, taking all the precautions described in Part 1.3, Section D, paragraph 1 (Note b). Ideally only one clear BOD bottle (called hereafter LB) and one opaque bottle (called hereafter DB) need be filled but it is strongly recommended that, where possible, duplicates be analysed to ensure the detection of gross errors and to improve the overall precision of the technique. ( in Section A will then equal 1.41.) If a result for both net photosynthesis and for respiration is required (see later) fill a third clear bottle (called hereafter IB), preferably in duplicate. 

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