How does a compensated Thorpe tube differ from an uncompensated one?

A compensated Thorpe tube differs from an uncompensated one primarily in how it is designed to measure gas flow accurately under varying pressure conditions. In a compensated Thorpe tube, a needle valve is typically positioned after the float. This design allows the tube to maintain accurate flow measurements even when upstream pressure changes.

When the needle valve is located after the float, it helps counteract the effects of pressure variations that can affect the reading of gas flow. The compensated design provides a more consistent and reliable flow rate measurement, which is critical in medical scenarios where accurate gas delivery is necessary.

On the other hand, an uncompensated Thorpe tube, lacking this design feature, may yield less accurate readings when pressure fluctuations occur, as it does not account for the changes in pressure upstream. Therefore, the placement of the needle valve is a key distinguishing feature of compensated Thorpe tubes that enhances their measurement accuracy.