Air bubble detector for blood transfusion unit - with IR rays passed through catheter tube by air bubble to be picked up by detector which actuates alarm and cuts off blood supply

摘要

The detector is fitted to a blood transfusion unit to detect an air bubble passing through the catheter tube. It comprises a source emitting infra-red rays which are focused onto the catheter. When blood is passing only, these rays are blocked and not directed onto a detector cell on the opposite side. If air passes, the rays activate the cell and a signal is transmitted through an inverter and into a voltage comparator. This closes another switch which is held by a thyristor until manually released. Simultaneously, visual and audible alarms are energised and the blood supply is cut off.