EUTECH INSTRUMENTS CD 650, Instruction Manual

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Figure 61 :Concentration Measurement Screen
3.2 Dissolved Oxygen Probe
3.2.1 Dissolved Oxygen Principle
The probe is a galvanic measuring element which produces an output
proportional to the oxygen present in the medium in which it is placed. The
galvanic probe design lets you take measurements immediately – without
the typical 15 minute wait of other dissolved oxygen probes.
The probe consists of two parts:
ƒ An upper part consisting of an anode, a cathode, and cable.
ƒ
A lower part consisting of a membrane cap, membrane, and electrolyte
solution.
Oxygen diffuses through the membrane onto the cathode, where it is
consumed. This process produces an electrical current which flows through
the cable to the meter. The electric current produced is proportional to the
oxygen that passes through the membrane and the layer of electrolyte.
This makes it possible to measure the partial pressure of oxygen in the
sample at a given temperature.
Item Description
1 Measurement mode indicator
2 Appears when the reading is stable
3 Appears when the reading is on hold
4 Concentration reading
5 Units of measurement
6 Temperature reading & units
7 Temperature compensation mode
8 HI & LO Alarm limits
9 Alarm indicator
10 ppt indicator for input of salinity value
11 DO calibration point