Choose the Auto-Rejection System

The Auto-Reject System step is an optional step in the Sigmafine Balance, Mass Balance, Component Mass Balance and Energy Balance Analysis rules. This step removes the instrument it considers as the most likely cause of a fault from the reconciliation and recalculates the result.

Options of the auto-rejection include the following:

• Note the two most severe measurement errors in the analysis log.
• Note the two most severe measurement errors out of service.
• Repeat the reconciliation and marking out of service until the severity of the balance points is between –1 and 1, inclusive.

As Sigmafine progresses through the Model during a reconciliation run, it continues to collect data about each balance point (node, process and inventory) and each measurement (meter, transfer, and inventory).

Sigmafine uses auto-rejection to report measurements that exceed the range established by the confidence level. Auto-rejection is based on the measurement range set by the confidence level which, in turn, is determined by the tolerance and confidence limit. The default values are ±2 standard deviations (2σ) for the tolerance and 95% for the confidence limit, meaning that a measurement error greater than 2σ occurs only 5% of the time.

EXAMPLE

Consider a reported measurement of 1400 for a meter with a tolerance of ±70 (70 is the 2σ interval). So, σ = 70/2, or 35. With a tolerance of ±2 σ, Sigmafine assumes that 95% of all measurements associated with the meter fall within the range of 1330 through 1470. If the confidence limit is set to 0.99, fewer errors are reported since Sigmafine only reports those errors with a 99% certainty.

For information about configuring auto-rejection, see the description for the Diagnostic Level box on the 'Control Parameters' tab.