The sensors are electrochemical devices which generate a current signal output (typically uA) that is proportional to the amount of oxygen present in the application. When no oxygen is present, the output has a theoretical value of zero. Once oxygen from the application diffuses into the membrane, a signal is generated through a chemical reaction that occurs between the anode, cathode and electrolyte solution.
The main difference between the two measurement ranges is the amount of oxygen present. One can easily convert back and forth between the two, 20.9% is equal to 209,000 ppm of oxygen. PPM or trace oxygen sensors are usually used when oxygen is measured at less than 1000 ppm.
CO2 and H2S gas can have an adverse effect on the life of our oxygen sensors. If you have an application that might contain CO2 or H2S, please contact a sales representative and ask for our recommendations. In most cases, we can offer another sensor model or sample system recommendation to negate the problem.
All sensors are rated at 0°C (32°F) to 50°C (122°F)
Temperature influences the signal output at the rate of 2.54% per °C. Compensation is recommended.
Moisture does not damage the sensor, however build up of excess moisture can block the gas flow. Another issue to monitor is that moisture and other types of corrosive liquids can damage the electrical connections of the sensor rendering it non-responsive.
The maximum load is a flat 10K, however no load is recommended. It is also worthwhile to note that the sensors cannot handle a reverse current flow.
Calibration is recommended by using a certified span gas in the range of analysis. We recommend sourcing an O2 mixture that falls into the 80 – 100% of the range you are using. Calibration should be in intervals of 2 – 3 months or as required by your application.
This is really dependent on the specific sensor as each may have a different storage life. For a general rule, we like to store our acid electrolyte sensors for a maximum of 3 months (for use with CO2 or Natural Gas). For our standard trace sensors, they can easily sit on a shelf up to 12 months as they are packaged in a nitrogen purged bags. For some of the higher output percent sensors, we would recommend 6 months or less. For our long life percent sensors, 12 months. When it doubt, reference the specification sheet of the sensor you are using as that has a more definitive answer.