Two approaches are followed to the non-invasive measurement of pressure in tubes.

Where the requirement is to detect occlusions, Strain Measurement Devices can supply miniature force sensors mounted into a housing, which is closed onto the tube. The load-button of the sensor professional presses against the tube wall such that expansion in the tube due to pressure changes is measured by the sensor. The resulting signal is proportional to the pressure, if the correct pre-compression is applied to the tube. Accuracy achievable by this technique is approximately +-15% across a range of different tube materials, or +-5% for a single tube material.

The second approach is applied where a higher degree of accuracy is required than can be obtained by a sensor directly applied to the tube wall. In this case, a disposable set with a molded membrane is used and sensor contract to the membrane is made by a flat plate. The sensor acts as a pressure-summing element. Due to the very small full range deflection of the sensor, movement of the membrane is minimized, resulting in good linearity characteristics. In this particular case, the full range of the sensor is 1000 mbar. With an accuracy of +/-1 mbar.