What is the relationship between the needle valve and uncompensated Thorpe Tube?

The needle valve regulates flow before reaching the flow tube, which is crucial for controlling the amount of gas that enters the Thorpe tube. The uncompensated Thorpe tube relies on this regulation because it has no built-in compensation for back pressure. By placing the needle valve upstream, it ensures that the flow of gas remains consistent, enabling the Thorpe tube to provide accurate flow readings. This regulation is particularly important in applications where precision in gas delivery is required, such as in medical settings where patients rely on continuous and accurate flows of oxygen or other medical gases.