AS 3580.6.1:2016 pdf download.Methods for sampling and analysis of ambient air Method 6.1: Determination of ozone- Direct-reading instrumental method.
3 DEFINITIONS
For the purpose of this Standard, the definitions below apply.
3.1 FaIl time The time interval, after a step decrease in input concentration, between initial instrument response and 90% of final instrument response.
3.2 Full scale (FS) The nominated maximum concentration for which an instrument has been calibrated. The full scale is selected to cover the normal range of values expected in the sampling environment.
3.3 Interference equivalent Positive or negative instrument response caused by a substance other than the one being measured.
3.4 Lag time The time interval between a step change in input concentration and the first observable corresponding change in instrument response.
3.5 Level I calibration A simplified, two-point analyser calibration used when analyser linearity does not need to be checked or verified.
3.6 Level 2 check A simple check of an analyser’s response. These checks may be performed using non-certified test atmospheres (e.g. ozone generators).
3.7 Linearity The deviation of an analyser’s output from a linear best fit line when subjected to varying reference test atmospheres.
3.8 Lower detectable limit The minimum pollutant concentration that produces a signal of exactly twice the noise level.
3.9 Noise Spontaneous, short duration deviations in instrument output, about the mean output, which are not caused by input concentration changes. Noise level is determined as the standard deviation about the mean and is expressed in concentration units.
3.10 Parameter One of the characteristics related to an air sample, e.g. concentration of constituent or other quantifiable property (wind speed, temperature).
3.11 Parts per billion (p.p.b.) A ratio expressing the volume of gaseous pollutant contained in 1 000 000 000 volumes of atmosphere. It may be expressed in terms of microlitres per cubic metre since the values are identical. Alternatively, it is one thousand million times the ratio of the partial pressure of gaseous pollutant to the pressure of the atmosphere in which it is contained.
3.12 Parts per million (p.p.m.) A ratio expressing the volume of gaseous pollutant contained in 1 000 000 volumes of atmosphere. It may be expressed in terms of millilitres per cubic metre as the values are identical. Alternatively, it is one million times the ratio of the partial pressure of gaseous pollutant to the pressure of the atmosphere in which it is contained.
3.13 Precision Variation about the mean of repeated measurements of the same pollutant concentration on the same instrument, expressed as one standard deviation about the mean.
3.14 Proficiency audit An evaluation processes used to measure the performance or effectiveness of a measurement system including analysis and validation.
3.15 Range Nominal minimum and maximum concentrations that a method is capable of measuring. NOTE: The nominal range is specified by the lower and upper range limits in concentration units, e.g. 0 to 0.5 p.p.m.
3.16 Reference test atmosphere A test atmosphere containing a known concentration of pollutant.
3.17 Rise time The time interval, after a step increase in input concentration, between initial instrument response and 90% of final instrument response.
3.18 Span drift The percentage change in instrument response to an on-scale pollutant concentration over a period of’ continuous unadjusted operation.
3.19 U95 A measurement of uncertainty at a confidence interval of 95% according to ISO/IEC Guide 98-3.
3.20 Zero drift The change in instrument response to zero pollutant concentration over a period of continuous unadjusted operation.
4 PRINCIPLE
For ultraviolet absorption type instruments, the sample air containing ozone is passed through a measurement cell. Ultraviolet energy of wavelength 254 nm passes through the cell and the resultant energy is measured using a photodetecting device. The degree of absorption is dependent on the number of ozone molecules in the path, i.e. it is dependent on the length of the cell and is flow independent. The absorption is compared to the absorption with zero ozone and the difference in energy received at the detector is converted into an electrical output and measured.AS 3580.6.1 pdf download.