| 摘要 |
The accuracy of measurements of changes in air volumes within a plethysmograph is improved by addition of a manifold to provide a common source of exterior air to the plethysmograph test and reference chamber. The preferred plethysmograph includes test and reference chambers divided by a common separator wall, pneumotachs in communication with the chambers, and a differential pressure transducer having a first inlet in communication with the test chamber and a second inlet in communication with the reference chamber. The manifold includes an exterior air inlet and a passageway extending between the two pneumotachs and the air inlet. The passageway may be in the form of separate tubes or conduits, or a common housing covering the pneumotachs. Preferably, the distances from the exterior air inlets to the two pneumotachs are approximately the same.
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