Differential Pressure (DP) Flow meters are popular for being relatively simple, reliable and inexpensive. Their principles of operation are relatively easily understood. However, traditionally there has been a misconception that no DP meter self-diagnostic capabilities exist and as such only upgrading to newer ultrasonic or Coriolis technology can help bridge this gap. In 2008 & 2009 a generic Differential Pressure (DP) meter self-diagnostic methodology [1,2] was proposed to the industry.