This slide shows a bypass set-up of flow measurement using an orifice in the main channel flow path. The orifice restricts flow just enough to cause a differential pressure, proportional to flow rate, to exist on either side of it. This differential pressure causes gas to flow through the D6F-P flow sensor, again proportional to the flow rate in the main flow path, from the high pressure side of the orifice to the low pressure side. The end result is a flow sensor that can measure, with proper calibration, a wide flow rate range without being in the main flow path.