This sensor is a small, semi-sealed, cylindrical device that contains two different electrodes, a cathode and an anode and an aqueous electrolyte. This electrolyte is usually potassium hydroxide. An oxygen molecule diffuses on one side of the sensor and permeates through. The molecules are reduced at the cathode and form a positively charged hydroxyl ion. The ion then migrates to the anode where oxidization takes place. The reaction then produces an electrical current which is proportionate to the oxygen molecules. The current is measured and displayed on the screen. The ambient temperature electrochemical sensor, commonly referred to as the galvanic sensor, is a good choice for the following reasons. It has a long life and produces accurate measurements of the oxygen amounts. It is also recognized for its fast response times.
This is a cylindrical container with a glass dumbbell placed inside. The dumbbell is filled with an inert gas and is suspended on a tight platinum wire. This wire has a non-uniform magnetic field. Since the dumbbell is suspended from the wire, it is allowed to move freely. When oxygen passes into the container it is attracted to the higher magnetic field because of its high magnetic susceptibility. This causes the dumbbell to rotate. A precision optical system measures the degree of the rotation using a light source, a photo diode and an amplifier circuit. Then an opposing circuit is used to restore the dumbbell into its proper position. The current required to put it back into its regular position is proportional to the amount of partial pressure oxygen. Then it is displayed electronically as the percent of oxygen. The paramagnetic oxygen sensor is quite good for a few reasons. First of all, its response time characteristics are good and it uses no consumable parts. Therefore, the sensor's life is quite good. It also offers extremely precise percentages of oxygen.
This is an electrochemical sensor that is based on the Nernst principle. It uses an electrolyte that is fabricated from zirconium oxide that has been stabilized with yttrium oxide. The zirconium oxide probe is plated with platinum on both sides and serves as the sensor electrodes. For the sensor to work correctly, it must be heated to 650 degrees Celsius. If it is heated, then, on a molecular level, the zirconium lattice becomes porous. Based on the partial pressure of the oxygen, this allows oxygen ions to move freely from a higher concentration of oxygen to a lower one. This pressure is created by exposing an electrode to 20.9 percent air and the other to the real oxygen. The movement of oxygen ions on the electrodes creates a voltage based on the pressure and displays it on a screen. This is one of the good attributes of the sensor. It displays 100 percent oxygen and it can also show parts per billion concentrations. Another excellent feature is that it displays amazing response time characteristics.