WATER PRESSURE-RESISTANT TURBIDIMETER

PURPOSE:To prevent the lowering of the detection senstivity due to the increase in thickness of a window glass, and provided a water proof turbidimeter with a window glass increased in thickness, by axially changing the position of the light source center of a light-emitting diode in accordance with the thickness of the window glass. CONSTITUTION:A turbidimeter detection section 8 is immersed in a water- measuring tank 1, and a light-emitting diode 14 is turned ON. The light beam is scattered, and the beam component entering a window glass 12 is detected by means of a detecting light-receiving element 15. A part of the emitted light beam is passed through a bore 26 in a comparing block 25 and is detected by means of a comparing light-receiving element 16. A part of the beam of light emitted from the light-emitting diode 14 is reflected by the interface between the window glass 12 and the liquid to enter the detecting light-receiving element 15 and lower the snesitivity of detection of the scattered light. Therefore, in accordance with the thickness of the window glass 12, the light-receiving element 15 is axially moved by a predetermined value to prevent the lowering of the sensitivity. In addition, increasing the window glass 12 in thickness permits an improvement in water resistance.