The APOA-370 continuously monitors atmospheric ozone concentrations using a cross flow modulated ultraviolet absorption method. The APOA-370 employs an independent, internal dry-method sampling device to achieve the highest levels of sensitivity and accuracy. The dry method, due to its minimal maintenance requirements and capability of continuously monitoring and instantaneously analyzing gases in their unaltered state, has been a preferred method for monitoring the atmospheric pollution.
Cross flow modulation type, Non dispersive ultra-violet absorption method NDUV)
The ultra-violet absorption method works on the principle that ozone absorbs ultra-violet rays in the area of 254 nm. Measurements are taken from continuous, alternate injections of the sample gas and the reference gas into the measurement cell, controlled by a long-life solenoid valve. The cross flow modulation method is characteristically zero-drift free. A comparative calculation circuit automatically compensates for all fluctuations in the mercury vapor light source and in the detector. This means that, In principle, the APOA-370 makes it possible to carry out zero-span drift free, continuous measurements. In addition, HORIBA'S unique de-ozonizer for the comparison gas line is unaffected by interference elements or moisture retention, prolonged, stable measurement is possible.