| 摘要 |
PURPOSE:To abolish the support member for supporting one end part of a light pervious body and to widely take the distance range between the surface of a light emitting body and the surface of the light pervious body contacted with a measuring liquid, by fixing only the other end part of the light pervious body to the member for supporting the light pervious body. CONSTITUTION:A liquid mixture of petroleum fuel and alcohol is contacted with one side surface of a light pervious body 4 and the quantity of light emitted from a light emitting diode 35 and passing through the light pervious body 4 is measured by a measuring photodiode 54. That is, by utilizing the change of the critical angle at the contact part of the light pervious body 4 with the liquid mixture with the compositional change of the liquid mixture, the mixing ratio of the liquid mixture is detected on the basis of the value measured by the measuring photodiode 54. The light pervious body 4 is fixed to a light pervious body support member 27 only at one end thereof.
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