Gross​.Error

The Gross.Error menu item opens the gross error list for active model in the left side of the drawing canvas.

Since measurements of process variables, such as flow rate, inventory, concentration and temperatures, are subject not only to measurement error, but also to process variability, we cannot expect that any set measurements will obey the laws of conservation. Such errors would usually be expected to be random – that is to have an expected value of zero – but occasionally we find biased errors with expected values other than zero. Moreover, there are also many possible forms of errors such as missing flow, balance model problem etc. due to missing input data, process leaks and incorrect balance model.

Such gross errors can be of the following three types.

• Balance model error due to balance points consisting of only input flows or output flows.

• Missing flow error due to missing input data and process leaks.

• Faulty meters due to bias or malfunction of instruments, inadequate calibration or lack thereof, or poor sampling.

Data reconciliation is the procedure of optimally adjusting measured data so that the adjusted values obey the conservation laws and other constraints, while staying as close to the actual measured values as possible to retain a maximum degree of accuracy. Fortunately, there is redundancy of measurement in a typical plant, so the adjustments which bring measured values into harmony with each other result in greater overall accuracy.

The following procedure describes how to show the gross error list:

1. Select the Run menu.

2. On the Run menu, in the Show group, select Gross.Error.

   The gross error list appears in a panel on the left side of the screen.