What device is commonly used to facilitate flow measurement in piping systems?

The correct choice is a Venturi tube, which is widely used to facilitate flow measurement in piping systems due to its ability to provide accurate measurements based on the principles of fluid dynamics. The Venturi effect occurs when fluid passes through a constricted section of pipe, leading to a decrease in pressure and an increase in velocity. This relationship allows for the calculation of flow rate based on the difference in pressure measured at two points in the tube, using Bernoulli's equation.

Using a Venturi tube is advantageous because it creates a minimal obstruction to the flow, thus reducing pressure losses and potential turbulence, which can be important in many applications. It is especially effective in applications requiring a reliable and low-maintenance solution for flow measurement.

The other devices mentioned have different primary functions. A pressure gauge measures the pressure of the fluid rather than directly measuring flow. A flow meter, while also used for measuring flow, encompasses a broader range of types and technologies and may not refer specifically to the principle of operation exemplified by the Venturi tube. A flow switch is designed to detect the presence or absence of flow rather than to measure the actual flow rate, making it unsuitable as a device for flow measurement in the same context as a Venturi tube.