A liquid flow rate detector and controller having a microprocessor that senses the rate of drops falling in a monitoring balloon on a fluid tube. A light emitter/detector diode pair detects drops as they fall in the balloon, which are timed by the microprocessor. The device has first and second switches...http://www.google.co.uk/patents/US6491659?utm_source=gb-gplus-sharePatent US6491659 - Liquid flow rate controller
