Apparatus and method for sensing fluid level

摘要

An array of four infrared LEDs and an array of four phototransistor receivers with each LED and phototransistor mounted inside a light baffle. The LEDs are positioned in a substantially vertical array just outside one side wall of the cassette. The vertical line on which the LEDs are arranged is substantially parallel to the direction in which the fluid/air interface moves within the cassette. The LEDs are aimed upwardly at an angle of approximately 20 DEG from horizontal. A corresponding substantially vertical array of four phototransistor receivers is mounted outside the cassette opposite the LEDs such that each of the receivers is aimed at its corresponding LED.