What is a requirement for a Thorpe Tube to operate correctly?

The requirement for a Thorpe Tube to operate correctly is that it must be attached to a source at a constant pressure of 50 psig. This specific pressure setting is crucial because the Thorpe Tube measures gas flow based on the difference in pressure; it provides an accurate and consistent measurement of the flow rate as the buoyancy of the float inside the tube is affected by the pressure of the gas. When connected to a source with a stable pressure, the flow readings remain reliable and representative of the actual gas flow being delivered.

In a medical setting, where precise gas delivery is often critical, having a constant pressure allows for effective management of gas flow to patients or equipment without variations that could arise from fluctuating pressures. This standard ensures safe and optimal performance of the flowmeter.

The other options do not align with the operational requirements of the Thorpe Tube. For example, being adjustable to any pressure or working independently of pressure sources would compromise the fundamental design of the device, leading to inaccurate flow readings. Additionally, while digital flow measurement might offer advantages in some contexts, it is not a requirement for the operation of a standard Thorpe Tube, which is based on a mechanical principle involving the movement of a float.