Xylem SI Analytics Lab 745 Manual De Instrucciones página 55

8 Meter Lab 745
8.1 Areas of use
The oxygen meter is used to determine of dissolved oxygen as per the German Standard procedures
for water, wastewater and mud examination as per DIN EN ISO 5814:2013 and combines the
advantages of compact dimensions with the precision and the comfort of a lab meter. It is excellent for
the control of the oxygen content in surface water, in wastewater and for the wastewater treatment.
Simultaneous oxygen and temperature measurement, high measuring accuracy, multifunction display,
simple air calibration, integrated data logger and the robust aluminum housing are trademarks of this
meter.
8.2 Basic model
The basic model meter Lab745 is delivered with the sensor Ox1113T. This combination meets the
requirements for the determination of the dissolved oxygen; electro-chemical procedure as per DIN EN
ISO 5814:2013. If it is connected to the sensor, the meter will also capture the mass concentration of
the dissolved oxygen in mg/l oxygen and the oxygen saturation index (% saturation) and the
temperature.
8.3 Oxygen sensor Ox1113T
The sensor is based on an amperometric measuring cell with a pt cathode as an indicator electrode
and an Ag/AgCl anode as a counter electrode. Both electrodes, including the cell electrolyte, are
separated from the measuring medium by a mostly chemically resistant, but molecular oxygen
permeable membrane. With this, the interfering components in the measured material cannot impair
the functionality of the electro-chemical measuring cell. With the polarization voltage of approx. 700
mV between the Pt cathode and the Ag/AgCl anode, the oxygen diffused from the oxygen-containing
material through the polymer membrane is reduced cathodically to hydroxide ions. The oxidation
causes an equivalent number of silver ions on the anode, which react with the chloride ions of the
electrolyte solution. The flowing diffusion stream is proportional to the oxygen partial pressure in the
sensor. The oxygen sensor consists of a shaft and a base, including electrode system and membrane
head. The base contains a platinum cathode and Ag/AgCI: anode plus a temperature sensor.
The oxygen permeable polymer membrane is integrated into the membrane head. The extremely
stable multi-layer membrane used here ensures reliable measurements over long time periods without
exchanging the membrane head and electrolyte.
Membrane head Base Shaft Fixed cable with plug
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