OG-3 Calibration using the UV-100 Ozone Analuzer
Tech note from EcoSensors
The Eco Sensors UV-100 calibration can be fairly accurately monitored using the Eco Sensors OG-3 Calibration Checker if the calibration of the OG-3 is checked and adjusted for accuracy at the user's altitude. The OG-3 is calibrated in Eco Sensors' laboratory at 2,100 meters. At lower altitudes the OG-3 will generate ozone at a slightly higher concentration than the standard .1 ppm due to the higher molecular density of air at lower altitudes. This difference in OG-3 output is not significant for checking the calibration of the semiconductor sensor (HMOS) Eco Sensor instruments, but may warrant slight adjustment for checking the calibration of the higher precision UV-100.
First, the OG-3 and UV-100 should have their calibrations synchronized when both instruments arrive from the factory to a calibration site with approximately the same altitude as the end user of the UV-100. This calibration checking should be done in relatively gas free air in an air conditioned room with essentially no direct outside air present.
- Allow a one hour warm-up for both the OG-3 and the UV-100
- Attach the short 10 mm (3/8") outside diameter tube to the UV-100 air filter input barb and fit its other end just inside the 10 mm hole on the bottom of the OG-3. Do not extend it far into the OG-3. A few mm is sufficient. Any further in will reduce the calibration accuracy.
- After at least one minute, read the UV-100. It will typically be slightly different than .1 ppm - usually slightly higher. Align the tubing in the OG-3 hole in step (2) to maximize the UV-100 reading without pushing the tubing more than a few mm into the OG-3.
- Record the UV-100 reading. For example, if it is .11 ppm, future calibration check readings can be adjusted downward by .01 ppm.
- Alternately, the OG-3 calibration can be slightly adjusted for greater accuracy by:
- Remove the black round tape patch on the calibration access hole near the power jack input.
- The reading on the UV-100 will go down slightly because of the ozone leak through the calibration access hole.
- Slightly adjust the calibration pot with an instrument screwdriver so that the apparent OG-3 output declines by the offset factor described above - .01 ppm in our example.
- Replace the access hole patch and check for .1 ppm output as read on the UV- 100.