23
Figure 16 Multiple Timer Method
In order to show the concentration-time curve as shown in Figure 15 during the last
timing step, The SP-910 must be zeroed using the prepared blank before the last
timing step. Thus, the last timer button will not be selectable until the SP-910 has been
zeroed using the prepared blank. Multi-timing step Hach® methods require zeroing the
colorimeter using the prepared blank after the last timing step is completed. The SP-
910can optionally be re-zeroed using the prepared blank after the last timing step. The
blank value measured will be subtracted from the concentration value measured at the
end of the last timing step. Optionally, the READ button could be pressed to read the
prepare sample again.
The following procedure is typical for methods having two-timing steps:
1. Press the TMR1 button to start the first timer. Complete the necessary
operations to prepare the blank and the sample.
2. Place the prepared blank into the SP-910 sample vial compartment and
press the ZERO button.
3. Place the prepared sample into the SP-910 sample vial compartment and
press the TMR2 button to start the second timer. The SP-910 will display the
measured concentration as a function of time as shown in Figure 15.
4. When the timing step is completed, the measured concentration will be
displayed on the top right of the screen. The timing step could be terminated
earlier by pressing STOP button.
5. Optionally, The SP-910 can be re-zeroed using the prepared blank after the
timing step is completed or terminated. The blank reading will be subtracted
from the measured concentration value, and the displayed concentration
value on the top-right corner will be updated. This step is optional. It is only
necessary if the prepared blank changes its color during the timing period.
5.7 Advanced Methods
The SP-910 provides 7 LED wavelengths and can measure absorbance values at
multiple LED wavelengths. Consequently, The SP-910 can provide many predefined
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