USF Wallace & Tiernan DEPOLOX 4, Руководство пользователя

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3.2 THEORY OF OPERATION
(see BZ-1150/1-5/E, fig. 2, 2A-2F)
The DEPOLOX 4 measuring cell consists of a 3-electrode system with external
potentiostatic closed-loop control. The working electrode and the counter electrode
(BZ-1150/3-5/E, fig. 2D, item 1 and BZ-1150/2-5/E, fig. 2B, item 2) of the half-ring type
are made of a platinum alloy. A silver/silverchloride electrode serves as reference
electrode (BZ-1150/2-5/E, fig. 2B, item 3); the contact between reference electrode and
sample water is established by two membranes (BZ-1150/2-5/E, fig. 2B, item 7). The
reference electrode is mounted in PVC brackets and completely submerged in electrolyte
(BZ-1150/2-5/E, fig. 2A/B, item 60). The electrolyte container is transparent, thus
enabling a visual check to be made of the amount of electrolyte in the reservoir.
Replenishment of the electrolyte is possible without shutting down the measuring cell
system. A membrane in the plug of the electrolyte reservoir provides the necessary
equalization of pressure (BZ-1150/2-5/E, fig. 2A, item 17).
The measuring cell is connected to a digital measuring amplifier which maintains an
adjustable constant potential (Upot) between working and reference electrodes by means
of potentiostatic closed-loop control.
About 33 l/hr of the water to be analysed flows past this system of electrodes. The
current generated in the measuring cell is directly proportional to the concentration of
the oxidising agent in the sample water. This current is then passed to the
microprocessor-based electronic system for processing.
The surfaces of the electrodes are continuously cleaned by a special kind of cleaning
grit in the electrode cell. The transparent plexiglass body of the cell makes it possible
to observe the circulation of the grit in the cell.
An integrated flow regulator (BZ-1141/E) ensures a constant sample water flow of about
33 l/hr.
If desired, electrodes for pH-value and Redox measurement can be inserted into the
two holes (BZ-1150/2-5/E, fig. 2A, item 48) in the removable cover of the measuring
cell. This means that the DEPOLOX 4 measuring cell can be augmented with extra
measuring devices without any additional piping.
The following features of the DEPOLOX 4 ensure accurate, repeatable measured
data and reduce the frequency of zero point recalibration:
- potentiostatic control
- continuous hydromechanical electrode cleaning system
- regulated sample water flow.
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