Which device would NOT be considered a part of a pressure control system?

A flow meter is primarily used to measure the flow rate of a substance, such as gas or liquid, and does not actively control or manage pressure within a system. It provides necessary data for monitoring the flow, but it does not have the function of regulating or controlling pressure levels, which is essential in pressure control systems.

In contrast, a pressure regulator adjusts the pressure coming from a source to a desired level. A compressor increases the pressure of a gas by reducing its volume, which is a critical function in managing system pressure. A safety valve serves to release pressure when it exceeds a certain threshold, preventing potential hazards associated with overpressure situations. Each of these devices plays a direct role in maintaining and controlling pressure, while the flow meter is external to that specific function.