ELECTRONIC_TURBIDIMETER

Published:2009/7/15 22:40:00 Author:Jessie | From:SeekIC

A turbidimeter is a scientific instrument used to measure the cloudiness of solutions，such as water，if you measure the amount of scattered light，you can measure the turbidity. Paint the inside of the test－tube holder flat black Glue a cadmium sulfide photoresistor (R2)to a cardboard disk，and glue the assembly to the open end of the 90°tube Next，cement a biconvex lens (one that curves outward on both sides) to the bottom of the test-tube holder. Power up I1，a 12-V， 1-A automotive light bulb, and hold it at various distances below the biconvex lens. Find the distance at which a beam of light comes straight up the tube or converges slightly, but does not diverge. Mount the lamp and play it on the 100-μA meter; the resistors on the rotary switch set the sensitivity or attenuation. Power is supplied to the circuit by two 9-V batteries in a split supply; I run the lamp off a separate 12-V supply. If you want truly calibrated readings, you'll need to buy a turbidity standard solution, available in JTU (Jackson Turbidity Units) and NTU (Nephelos Turbidity Units), from a science-sup-ply company. In operation, zero the meter to a clean-water blank, note the reading from a known standard, note the reading from the unknown sample, and calculate the sample's turbidity, based on the needle's position.



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