DISSOLVED OXYGEN SENSORS COG-1, COG-1t

COG-1 and COG-1t oxygen sensors are designed for measurements of oxygen concentration in natural water, sewage or saline water during laboratory and field measurements. They can also be used for measurements of oxygen in the air.
COG-1t is equipped with a built-in temperature sensor.

Characteristic features:

Wide measuring range which enables usage in highly oxygenated (supersaturated) water.
High measurement accuracy at an affordable price in comparison with offers of other manufacturers.
Easy maintenance and short calibration time make working easier.
This sensor may work for many years, just the user has to remember about simple periodical maintenance operations.
In case of measurements of oxygen in mg/l the temperature, salinity and atmospheric pressure influence needs to be taken into consideration. The Elmetron meters enable manual or automatic adjustments and corrections.
The teflon foil membrane provides great chemical resistivity, high selectivity and good oxygen permeability. The membrane is mounted in a cap, which is easy to replace.
The sensor is equipped with internal temperature compensation system, which makes corrections dependent on the temperature and membrane permeability.
Negatively charged silver cathode has higher resistance to contamination with sulphides, what makes this sensor very useful in measurements of heavily contaminated liquids like industrial and municipal waste water.
High accuracy and repeatability of readings can be obtained under condition of a flow of the sample, in close proximity to the membrane (a few cm/s). The lack of flow will result in lowering the reading value due to gradual oxygen consumption, by the sensor, in proximity to the membrane. In vessels without flow a slow, circular movement imitates it and provides stability of reading, using a stirrer can also solve this problem.
The sensors are characterised by a long term stable signal what makes using it much easier and lowers the costs of maintenance and use.
For oxygen measurement in the air one point calibration at 20,9 % has to be done, for oxygen measurement in water one and two point calibration is possible at 0 %, and next in the air – at 100 %.
Gases such as chlorine, sulphur dioxide, hydrogen sulphide, amines, ammonia or carbon dioxide may cause interference in the measurements.

The COG-1 sensor works on the galvanic cell principle. It consists of a silver cathode and a zinc anode placed in the electrolyte solution, separated from the measured solution by the membrane, which is permeable for oxygen. The oxygen diffuses through the membrane and is reduced on the cathode, what generates voltage proportional to the partial pressure of the oxygen at current temperature.

TECHNICAL DATA

Measuring range	0 ÷ 100 % in the air 0 ÷ 600 % in water 0 ÷ 60 mg/l water
Accuracy	at calibration temperature: ±1 % *
Temperature measurement accuracy	in range 0 ÷ 40 °C ±0.5 °C
Acceptable temperature of measured solution	0 ÷ 40 °C
Temperature compensation range	0 ÷ 40 °C (for mg/l measurement)
Signal of the probe in solutions (in 20 °C )	In 100 % O₂ saturation: 20 ÷ 25 mV, in 0 % O₂ saturation: max 0.3 mV
Signal drift	0.7 % / 24 h
Time of response T₉₉	below 1 minute
Internal compensation	yes (thermistor)
Built in temperature probe	yes, Pt-1000B (COG-1t)
Cathode material	silver
Anode material	zinc
Membrane material	teflon foil
Body and membrane cap material	PVC
Electrolyte	KCl 0.5 mol/l
Body diameter	12.0 ±0.5 mm
Body length (to handle)	120.0mm ±5 mm
Cable length	above 1 m
Connector	BNC-50 / RCA (chinch COG-1t for temp.)

*	By the difference ±5 °C accuracy: ± 3 %, by the difference ±10 °C accuracy: ±5 %.