Method for in-situ calibrating a differential pressure plus sonar flow meter system using dry gas conditions

A method for calibrating a flow metering system, comprising the steps of:

• measuring a characteristic of a dry gas flow using a differential pressure flow meter, and producing a first output data representative of the characteristic;
• measuring a characteristic of a dry gas flow using a SONAR flow meter time during the dry gas period, and producing a second output data representative of the characteristic;
• determining a dry gas offset between the differential pressure flow meter and the SONAR flow meter based on the first output data produced by the differential pressure flow meter and second output data produced by the SONAR flow meter;
• and
• calibrating the flow metering system using the dry gas offset,
• wherein the calibrating of the flow metering system includes calibrating at least the differential pressure flow meter to decrease any difference that may exist between the first output data and the second output data.

A fluid flow metering system, comprising:

• a differential pressure flow meter operable to measure a characteristic of a fluid flow, and produce a first output data representative of the flow characteristic;
• a SONAR flow meter operable to measure a characteristic of a fluid flow, and produce a second output data representative of the flow characteristic;
• and
• a processor adapted to determine a dry gas offset between the differential pressure flow meter and the SONAR flow meter based on the first output data produced by the differential pressure flow meter and second output data produced by the SONAR flow meter, and to self calibrate using the dry gas offset, the self calibration including a calibration of the differential pressure flow meter.