Hach 1950Plus, Инструкция по эксплуатации инструмента, Страница: 20 / 188

Page 20
Analysis Process
UVTOCIntroduction.fm
Section 1
1.3.3 Front Panel
Detailed information on the LEDs,
keypad, and menu functions can be
found in
Section 5 on page 63 .
The two-line, 16-character alpha-numeric backlit display is mounted on the
rear of the 8000 Display/Controller PCB assembly. Refer to
Figure 4 .
Three front-panel LEDs indicate analyzer status. These will normally be
extinguished unless they represent the assigned condition. A1 and A2
indicate that a first level or second level rising nonlatching alarm exists. F will
illuminate if a fault or maintenance request has occurred.
The user keypad consists of four membrane button keys. These buttons will
have different functions depending on whether or not the analyzer is in the
menu system. Combination button presses will result in different functionality,
dependent on the software state.
Figure 4 Front Panel
1.4 Analysis Process
The analysis takes place in a two-stage process. First, the Total Inorganic
Carbon (TIC) is removed by acidification prior to the analysis, leaving an
inorganic-free sample. Secondly, the analyzer converts the carbon in the
sample to CO
2
in a low temperature UV reactor. An IR detector measures the
CO
2
, which is proportional to the carbon concentration in the sample.
This TOC measurement is sometimes referred to as NPOC.
Acidification
The sample is acidified with phosphoric acid in the TIC sparger. This converts
the inorganic carbon to CO
2
. This CO
2
is removed from the sample at the
GLS and is vented to the atmosphere. The sample, which now contains only
organic carbon, is pumped from the TIC sparger to the UV reactor for further
analysis. (Only TOC analysis requires acidification. If you are measuring TC,
your analyzer will not acidify the sample.)
1. Alphanumeric Display Window 2. Tactile Membrane Keypad 3. Three Analyzer Status LEDs
Ctrl Enter
A1 A2 F
Escape
Program Mode
1 3
2