Endress+Hauser CCS120D, Руководство по эксплуатации

Страница: 9 / 44

CCS120D Product description
Hauser 9
In this context, the following compounds are referred to collectively as total chlorine:
• Free available chlorine: hypochlorous acid (HOCl), hypochlorite ions (OCl - )
• Combined chlorine (chloramines)
• Organic combined chlorine, e.g. cyanuric acid derivatives
Chloride (Cl
- ) is not recorded.
The sensor is a membrane-covered, two-electrode sensor. A platinum working electrode is
used as the working electrode. A counter electrode coated in silver halide is used as the
counter and reference electrode.
The membrane cap, which is filled with electrolyte, constitutes the measuring chamber. The
measuring electrodes are immersed in the measuring chamber. The measuring chamber is
separated from the medium by means of a microporous membrane. The chlorine compounds
contained in the medium diffuse through the sensor membrane.
The constant polarization voltage present between the two electrodes causes the
electrochemical reaction of the chlorine compounds at the working electrode. Electron
donation at the working electrode and electron acceptance at the counter-electrode cause a
current to flow. In the operational range of the sensor, this current flow is proportional to the
chlorine concentration under constant conditions and is only slightly pH-dependent in the
case of this sensor type. The transmitter uses the current signal to calculate the measured
variable for concentration in mg/l (ppm).
3.1.2 Effects on the measured signal
pH value
pH dependency
The sensor is specified for the pH range of pH 5.5 to 9.5. The measuring signal is practically
independent within this range. However, if the pH increases from pH 7 to pH 8 the measuring
signal for free chlorine is reduced by 10 %.
Flow
The flow to the membrane-covered measuring cell should be at least 15 cm/s and maximum
50 cm/s. The optimum flow velocity is in the 20 to 30 cm/s range.
When using the CCA250 flow assembly, the minimum flow velocity corresponds to a volume
flow of 30 l/h (7.9 gal/h) (upper edge of float at the height of the red bar mark).