What device is commonly used to measure the flow of a gas?

The device commonly used to measure the flow of a gas is the orifice plate flow meter. This instrument operates based on Bernoulli's principle, which relates pressure drop to flow rate. As gas flows through the orifice, it experiences a reduction in pressure, allowing the measurement of flow based on this differential pressure.

Orifice plate flow meters are particularly effective for gases because they can accurately measure flow rates across various ranges and conditions, making them a staple in many industrial applications. Their design is straightforward and they can be easily integrated into existing piping systems.

In contrast, other devices like pressure gauges and thermocouples serve different purposes; pressure gauges measure pressure, while thermocouples measure temperature. Flow switches are designed to indicate the presence or absence of flow rather than provide precise measurements of flow rates. Thus, the orifice plate flow meter stands out as the appropriate choice for gas flow measurement in this context.