Instruction Manual
OCX 8800
The equipment measures oxygen percentage by reading the voltage developed across a heated electrochemical cell, which consists of a small
EMF = KT log10 (P1/P2) + C
Where:
1.P2 is the partial pressure of the oxygen in the measured gas on one side of the cell.
2.P1 is the partial pressure of the oxygen in the reference air on the opposite side of the cell.
3.T is the absolute temperature.
4.C is the cell constant.
5.K is an arithmetic constant.
NOTE
For best results, use clean, dry instrument air (20.95% oxygen) as the reference air.
When the cell is at operating temperature and there are unequal oxygen concentrations across the cell, oxygen ions will travel from the high oxygen partial pressure side to the low oxygen partial pressure side of the cell. The resulting logarithmic output voltage is approximately 50 mV per decade. The output is proportional to the inverse logarithm of the oxygen concentration. Therefore, the output signal increases as the oxygen concentration of the sample gas decreases. This characteristic enables the OCX 8800 to provide exceptional sensitivity at low oxygen concentrations.
The OCX 8800 measures net oxygen concentration in the presence of all the products of combustion, including water vapor. Therefore, it may be considered an analysis on a "wet" basis. In comparison with older methods, such as the portable apparatus, which provides an analysis on a "dry" gas basis, the "wet" analysis will, in general, indicate a lower percentage of oxygen. The difference will be proportional to the water content of the sampled gas stream.
The OCX 8800 combustibles sensor is a catalytic sensor consisting of two Resistance Devices (RTD). One RTD is the reference element covered with an inert coating. The other RTD element is active, coated with a catalyst. As the sample gases flow by the sensor, the combustible gases oxidize on the surface of the active element. The oxidation that occurs produces heat and a temperature rise in the active element. The temperature difference produces a resistance relationship between the two elements that is directly proportional to the concentration of combustibles in the sample gases.
