Xylem SI Analytics PL-S 82-225pHT VP ProcessLine Manual De Instrucciones página 20

pH - and Redox – electrodes
Range of application
• For long-therm monitoring and limit-value supervision of processes applied in chemical
industry, biotechnology, food industry and pharmaceutical industry.
• For water processing and supervision, for instance in sewage-water regeneration plants,
neutralisation plants or ground and surface waterbodies.
The area of application depends on the selected electrode group.
pH measurement
The pH value is a measure of the activity of the hydrogen ions in an aqueous solution, i.e. of
+
the acid or alkaline character of a solution. H ions cause a potential jump at the inner and
outer side of the glass membrane. The potential difference is being diverted as measuring
signal through the Ag/AgCl reference systems. Using the NERNST equation as a basis, a
measuring transducer will convert the voltage generated in this way (mV) into a pH signal.
Preparation and general observations
Please remove any irrigation cap on top of the membrane/Pt sensor. It contains a storage
solution (L 911 type). The electrode is now ready for measuring. Electrodes which were
stored dry should be irrigated for 24 hours in storage solution before being verified for proper
functioning by way of calibration or by performing a measurement in redox buffer solution. If
the deviation displayed by the electrode in this process should be excessive, please discard
it. A possible electrolyte solution shortage in the electrolyte space of the reference system
should be topped up. Please note the potassium chloride concentration to be observed for
the individual electrodes. In the case of low-maintenance electrodes with solidified
electrolytes such as a gel filling, Duralid or REFERID®, topping up is unnecessary. Irrigation
in storage solution is particularly important with these electrodes.
Measurement set-up and installation information
The pH sensor is part of a measurement device which consists of the following:
• pH electrode
• Measurement transducer
• Immersion, flow-through or interchangeable mounting assembly
• Measurement cable
Please note the operating instructions of the measurement transducer and the mounting
assembly as well as the configuration of the connection cable. The electrodes are not
suitable for overhead installation. The minimum out-of-horizontal installation angle is 15°.
Prior to installing the pH electrode, please check the connection thread for contamination and
adequate freedom of movement. Please observe the operating instructions of the instrument,
i.e. screw the electrode with a maximum of 3.5 Nm ("hand-tight") into the mounting assembly.
Connect the electrode and the measurement transducer using the connection cable provided
for this purpose. In this process, please note the configuration plan of the connection cable.
With regard to the installation of the sensors, please observe the applicable technical details
of the mounting assembly.
Electrical connection details
When connecting the sensor to the measuring transducer, the electrical connection
information provided by the manufacturer is to be observed.
Measuring the pH value
For calibration and measuring, please note the operating instructions of the measuring
device, too. To minimise the risk of a possible distortion of the measuring values, the
frequency of calibrating electrodes which are used under extreme circumstances or at the
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