Which instrument is used for both measuring flow and indicating pressure in fluid flow?

The instrument that can measure flow and indicate pressure in fluid systems is the Pitot Tube, Wedge Meter, and Orifice Plate. Each of these devices operates based on different principles but can serve both functions effectively.

The Pitot Tube, for example, measures fluid flow velocity by converting the kinetic energy of the fluid into potential energy, which is then used to calculate flow rates. It detects the difference between static and dynamic pressure, thereby providing a means to measure both flow and pressure simultaneously.

The Wedge Meter works by creating a pressure differential across a wedge-shaped obstruction in the flow stream, which allows for both flow measurement and pressure indication based on the flow rate through the device.

Similarly, the Orifice Plate provides a means to measure flow by creating a drop in pressure as fluid passes through it. The pressure difference across the plate can be used to infer both flow and the pressure conditions in the system.

Since all these instruments can be used for measuring flow and indicating pressure, selecting "all of the above" is accurate, as they all fulfill those criteria in various applications within process control and fluid measurement systems.