20
PHO
TOMETER MODE
Do not let the reacted sample stand too long after reagent is added. For best accuracy, respect the
timings described in each specific method.
It is possible to take multiple readings in a row, but it is recommended
to take a new zero reading for each sample and to use the same cuvette
for zeroing and measurement when possible.
Discard the sample immediately after the reading is taken, or the glass
might become permanently stained.
All the reaction times reported in this manual are at 25 °C (77 °F). In
general, the reaction time should be increased for temperatures lower
than 20 °C (68 °F), and decreased for temperatures higher than 25 °C
(77 °F).
Interference
In the method measurement section the most common interferences that may be present in a
typical water sample have been reported. It is possible that a particular application could introduce
other compounds that will also interfere.
6.4. TIMERS AND MEASUREMENT FUNCTIONS
Each method requires a different preparation procedure, reaction times, sample preparations, etc. If
a timer or timers are necessary for proper sample preparation, the
Timer
key will be available.
To use a reaction timer, press the
Timer
key.
The default timer will start immediately. To stop and reset the timer, press
Stop
.
If the selected method requires more than one timer, the meter will automatically select each timer
in the appropriate order. To bypass the default order, you may press the desired key to activate a
different timer (only while the current timer is stopped). Press
Continue
to start the active timer.
For some methods, the timer is only necessary after a
Zero
measurement has been performed. In
this case, the timer key will only be available after the
Zero
measurement has been performed.
If the method requires a
Zero
or
Read
measurement after a timer has expired, the meter will
automatically perform the appropriate action. Follow the instructions in the Method Procedure.
To perform a
Zero
or
Read
measurement, insert the appropriate prepared cuvette, then press the
Zero
or
Read
key. A
Zero
measurement must be conducted before
Read
measurements.