Lagged alternate check

The Lagged Alternate Check detects the drifting of values between two measurement readings.

It is performed after the data is loaded into the tables, and only if the following conditions are met:

• New Val1 or Val2 (corrected volume) is available.

• Gas Quality (GQ) or Meter Run is active.

• If the two readings have different times, this can be specified. For example, having a meter upstream of the meter that is being validated. The upstream meter is going to have a reading occurring at an earlier time than the meter that is further downstream.

• A meter can also be compared to station data.

The Lagged Alternate Check verifies the following values:

• Heating value

• Specific gravity

• Gas components

Using the Lagged Alternate Check, it is possible to compare stations against other stations. The Lagged Alternate Check compares the following station values:

• Volume

• Energy

• Mass

• Pressure

• Temperature

The following algorithm is used to detect drifting values:

Where:

• Val1 = Measurement data associated with this meter, GQ, or station.

• Val2 = Measurement data associated with the alternate meter, GQ, or station.

• Tol = Tolerance (% error) acceptable for the data check.

Meters can be checked against another meter or a station. You can configure these values to be checked: volume, energy, mass, pressure and temperature.

GQ fields can be checked against another GQ. You can configure these values to be checked: heating value, specific gravity and the component fields.

Stations can be checked against another station. You can configure these values to be checked: volume, energy, mass, pressure and temperature.

The processing will continue regardless of whether the outcome is true or false. If the statement within the algorithm proves false, then the system generates an event message for the values in question, and a problematic context record.