CHAPTER 14 - MEASUREMENTS IN PRESSURE CONDUITS
These meters measure part of the total flow which is allowed or forced through a small passageway by differential pressure across a fitting and returned to the main flow. Thus, these meters are sometimes called proportional, or shunt, flowmeters. The side flow drives an indicator or small water measuring device such as a propeller, vane, rotameter, or turbine meter. Indicators of the smaller flowmeter readings are related to total discharge by calibration. These reading devices display or indicate instantaneous rate of flow, totalized volume of flow, or both. Bypass meters are produced and sold commercially with calibrations and discharge tables.