For turbidity greater than 40 NTU, use undiluted stock solution. Do not use standards with flocculated suspensions. Switch the turbidimeter on and allow it to warm up. Put on disposable gloves. The lamp image should just fill the inside circle.
Adjustment is required if the image is off center, too large, or too small.
Pour standard into the sample cell to the fill mark. Select the desired NTU range. Set the calibration adjustment to equal the high value of standard for the range of interest. Before inserting the standard, ensure that no air bubbles are present. Adjust standardization control until the value on the meter equals the NTU value of the standard used.