To comply with internal procedures and ensure process integrity and quality, and/or comply with regulations and government mandates, fow meter users are often required to periodically validate and verify the meter’s calibration and operational integrity. Traditionally, the only way to meet this requirement was to pull the meter out of service and return it to a factory calibration center or a third-party calibration laboratory to have it checked. Clearly the expense and time to shut down the process, plus the labor to physically disconnect the meter and remove it, plug or by-pass the pipe, and to box and ship the meter, are very high. And after all this, to have the laboratory advise the meter’s calibration was still valid and no adjustments were needed, is exasperating. Further, many regulations and best practices recommend checking the fow meter in its actual operating environment rather than the pristine conditions of a laboratory. Until now this ability to feld-verify a fow meter’s calibration on site has been elusive and, while still installed in the process piping, virtually impossible.