LIQUID SURFACE LEVEL DETECTOR

摘要

PURPOSE:To eliminate inaccuracy of the detection due to dirt of an inner wall by detecting a liquid surface level from a relative vaue of the output of a plurality of photo detectors when they receive a light from a float provided in a long cylinder with a small reflection factor of the inner wall. CONSTITUTION:A flat 3 is placed free inside a long cylinder 1 formed with a small reflection factor of the inner wall while a light emitting diode 4 and two photo transistors 6 and 7 different in the directivity are arranged at the upper end thereof positioning at the top of a regular trangle. A light from the light emitting diode 4 is reflected on the top surface of the float 3 and detected with the photo transistors 6 and 7. A relative value of the variation factors of the photo transistors 6 and 7 is taken to detect the level of the liquid surface A. The reduced reflection factor of the inner wall of the long cylinder 1 can ensure the detection output almost free from the effect of the inner wall thereby enabling accurate detection for a long time.