Turn the unit on by pushing toggle switch (12) to ON position. Let it warm up for one minute.
When you release the ON/OFF toggle switch, it automatically returns to OFF position.
Push the on/off toggle switch(12) to the right to the ZERO CHECK position. Hold it there.
Turn the ZERO ADJUST knob(11) until the needle indicates 0.0 on the %T (percent transmittance) scale(14).
Release the on/off toggle switch(12). The procedure is complete.
18.104.22.168. Using the Spectrophotometer (fig. 2-5).
Individual test procedures (para 2.6.8) explain how the Spectrophotometer is used to measure the presence of specific
substances in water. Most tests using the Spectrophotometer include two measurements of the light passing through a
sample cell. The first measurement is made on a "blank." Typically a blank is an untreated sample of the water to be
tested. Deionized water is specified as the blank in a few tests. A second measurement is made on the water sample
after it has been treated to develop a color that is related to the concentration of the substance being tested for.
The inside of the cell holder should be kept clean and dry at all times. Water droplets in the cell
holder light slit, on the photocell window or on the sample cell itself will cause error in the
Reference Cell Adjustment. Follow the individual test procedure for preparing a "blank" or reference sample.
Zero adjust the unit. See para 22.214.171.124 above.
Insert the meter scale card(2) specified in the test procedure instructions into the slot on the left of the
When handling clean sample cells do not touch the two clear sides of the cells. If it is necessary
to hold the sample cells by the sides touch only the two opposite frosted-glass sides. Finger
prints on the clear glass will cause errors in readings.
Make sure the outsides of both sample cells(7) are clean and dry.
Set the wavelength dial(8) as specified in the test procedure.
The light shield lid must be closed for all measurements made with the Spectrophotometer.
Otherwise, stray light will interfere with readings or cause errors.
Lift the light shield lid(4). Hold the reference sample cell by the top lip and turn it so the clear sides of the
sample cell are the left and right sides relative to the Spectrophotometer panel. Gently lower the sample
cell into the well(5). Close the light shield lid(4).
Turn the LIGHT CONTROL knob(l0) left or right until the meter needle points to the reference value on the
scale(14). The reference value is usually, but not always, zero. See each procedure for the proper