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Ambient air contains about 20% oxygen and is essential for breathing, also for fish and other aquatic organism. Dissolved oxygen is the amount of free oxygen in water suitable for the breathing purpose. If there is not enough oxygen, it is letal to lethal to fish: the amount of 2 mg/l is deadly and the amount between 2 and 5 mg/l affects fish health.
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Different sensor types suit some applications better that than the others. These properties will be discussed later on the page, meanwhile the applications can be found from Figure 2.
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- Since the electrode consumes oxygen, readings are affected by flow across the sensor tip. Thus enough flow rate at the membrane (or sample renewal rate) must be ensured for accurate results.
Advantages
- Fast response time therefore best suited where fastest response time is necessary or for huge amount of measurments.
Galvanic Electrode
A typical galvanic electrode consists of a zinc or lead anode, a gold or silver cathode and an electrolyte solution (KCl or KBr). The principle of the galvanic sensor is that it uses 2 different types of metal and the difference in them with the electrolyte results in an electromotive voltage. This electromotive voltage is around 0.8 V which is enough to operate the sensor. Therefore the biggest advantage of the galvanic sensor is that there is no need for outside voltage source and there is no warm-up time.
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