The poppet of a pressure regulator is opened by which type of pressure?

The correct response is based on the function of a pressure regulator. The poppet of a pressure regulator is primarily influenced by the downstream pressure. In essence, the regulator's purpose is to maintain a set downstream pressure, ensuring that it stays constant regardless of variations in the upstream pressure. When the downstream pressure drops below the set level, the poppet opens to allow more flow from the upstream side, thereby increasing the downstream pressure until it stabilizes at the desired level.

Understanding the role of downstream pressure in controlling the poppet highlights the importance of maintaining consistent output pressure in various applications such as gas lines, fuel systems, or hydraulic circuits. The adjustment spring is indeed important as it sets the desired downstream pressure level but does not directly open the poppet. The upstream pressure and poppet spring also play roles in the operation of the regulator, but the direct action of opening the poppet is a response to changes in downstream pressure.