(c) For battery DC operation the second AC power cable (HC5)
must be disconnected from the amplifier board and the battery pack
cable (also marked HC5) connected at BC5 in its place as illustrated
in figure 2-12.
The primary AC cable between the case receptacle and
the power supply board and the line voltage plug should not be
(3) Sample Preparation.
The first task in any calorimetric test
is to prepare the water sample.
The applicable reagent or reagents
are added to provide the color indicator for the substance to be
If the standardizing solution to be used requires some
it too is prepared at this time.
Normally in the
preparation of the sample, a minimum waiting period must be observed
following the addition of the final reagent in order for the color to
There may also be a maximum time limit after which the
color will begin to fade.
it is important to take the read-
ings withing the time period specified in the test ot obtain accurate
Spectrophotometer in Use (fig. 2-11).
The next step in the
calorimetric test is to set up the spectrophotometer for the particu-
The standardizing solution (usually untreated water sample)
is placed in the cell holder and the lid closed, the appropriate meter
scale is inserted in the meter and the proper wavelength is dialed.
Then the instrument is zeroed and standardized.
(1) To zero the instrument, the light switch is held in the
zero check position while the zero adjust control is used to obtain a
zero transmittance reading (needle aligned with the mark at the extreme
left of the arc).
If a % Transmittance-Absorbance meter scale is
used, adjust for a % T reading.
The light shield lid must be closed for
(2) The instrument is standardized by setting the light switch
to ON and using the light control to obtain a meter reading equal to
value of the standardizing solution.
Normally the standardizing
solution is untreated sample water and the meter is adjusted for zero
mg/l (extreme right mark of the scale arc) reading.
does not need to be zeroed each time this is performed, but frequent
checks of the zero adjustment are recommended.
(3) The batteries are in good condition if the instrument can be
standardized as performed in each calorimetric test while the instru-
ment is on battery power.
If a zero mg/1 reading cannot be obtained
using the light control, the batteries may need replacing.
placing the batteries, change the instrument to operate on AC power
and verify that it can be standardized in that mode.
A darkened lamp
could be the cause of the inability to obtain the zero mg/l reading
(table 3-2, item 3, step 3).