Turbidimeter employing a semiconductor laser diode and a photodiode

In a turbidimeter for measuring a turbidity of a test solution to be measured i.e. culture solution in a fermentation apparatus, a semiconductor laser diode and a semiconductor photodiode are integrally arranged in a detection portion of the turbidimeter in such a manner that a laser beam emitted from the semiconductor laser diode is made incident upon the semiconductor photodiode through the test solution. Moreover, a protection circuit for the semiconductor laser diode and the semiconductor photodiode is also arranged in the turbidimeter to cut off a current flowed therethrough when an environmental temperature becomes above a predetermined temperature. Therefore, the turbidimeter can be made small in size and light in weight, and the turbidity can be measured accurately over wide range.