An electromagnetic blood flowmeter for measuring blood flow to the oral region of anaesthetized experimental animals

An A.C. electromagnetic blood flowmeter capable of recording the small volume flows occurring in the arteries supplying the oral tissues has been constructed. The cannula and the magnetic head construction require the interruption and cannulation of the vessels. The amplifier consists of five stages in a cascade arrangement and incorporates a small amount of negative feedback. The maximum amplifier gain is in excess of one million. The output, which is proportional to the volume blood flow, is recorded on an ink-writing oscillograph. The high amplifier gain and precise phase monitoring system permit blood-flow determinations as small as one millilitre per minute.