TM 10-6630-245-13&P
e.
Aged Chemicals. Some of the reagents have limited shelf lives and are not useful after their expiration date.
Check reagents according to the PMCS to avoid this problem.
2.6.2. Operation of Spectrophotometer.
2.6.2.1. Tests Using Spectrophotometer.
The Spectrophotometer is used for the following tests. These tests also require reagents and equipment which are stored
in the main carrying case of the WQAS-PM.
SPECTROPHOTOMETER TESTS
TEST
RANGE
TEST
RANGE
Fluorides
0.0 to 2.0 mg/l
Nitrogen, ammonia
0.0 to 2.0 mg/l
Iron, ferrous
0.0 to 2.0 mg/l
Nitrogen, nitrate
0.0 to 30.0 mg/l
Iron, ferric
0.0 to 2.0 mg/l
pH
4 to 10 pH units
Iron, total
0.0 to 2.0 mg/l
Sulfate
0.0 to 150.0 mg/l
Turbidity
0 to 500 FTU
2.6.2.2. Spectrophotometer Features.
In addition to the controls and indicators described in paragraph 2.1, the Spectrophotometer has several features that the
operator must be familiar with to operate the instrument. They are discussed below (fig 2-5).
a.
Sample Cells. Two identical sample cells(7) are used to hold treated and untreated water samples on which
measurements will be taken. The cells hold approximately 25 ml of water. Two opposite sides of the cells are
frosted. The other two opposing sides are clear. When handling the cells hold them by the lip or the frosted
sides. Touching the clear sides will leave finger prints that will interfere with measurements. In most test
procedures one sample cell well is used to hold a reference blank, usually untreated sample water. The other
cell is used to hold the treated sample water. The cells are optically identical and can be used interchangeably.
However, if one cell becomes damaged or scratched, they will no longer be identical and should be replaced.
b.
Storage Well for Meter Scale Cards. A storage well in the upper right corner(3) of the front panel is used to store
meter scale cards(2). This well is also used to store one of the two ac line-voltage-select plugs(l) that is not
installed within the unit.
c.
Sample Cell Well. The sample cell well(5) is the middle well of three wells on the right of the front panel, next to
the wavelength dial(8). Sample cells are put here for measurements and to set the meter for the reference
blank. Inside the sample cell well there are two optical windows. In one of these in the center of the left hand
side of the sample well is a vertical slit. The light source shines through this window. It then passes through the
sample cell. The second window is a round window on the right hand wall of the cell. This is the photocell
window. The photocell electronically measures the amount of light passing through the sample cell. The sample
cell should always be placed in the well with the two clear sides of the cell on the left and right. When not in use
one of the sample cells is stored in the sample cell well.
d.
Light Shield. A black lid(4) is hinged to the sample cell well(5). It is called the light shield lid. This lid should be
closed when taking readings or when adjusting the meter.
e.
Second Cell-Storage Well. This storage well (6) is at the lower right hand comer of the front panel. It is used to
store one of the sample cells when not in use.
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