BS EN 16253:2013 pdf download

BS EN 16253:2013 pdf download.Air quality —— Atmospheric measurements near ground with active Differential Optical Absorption Spectroscopy (DOAS)— Ambient air and diffuse emission measurements.
7 Procedure in the field
7.1 Installation and start-up 01 the instrument
The following aspects shall be specifically obseived during the mechanical installation of the optical components (.iducng a separate analyser unit, where applicable), as well as when setting up and adiusts’Ig a monitoring path. The manufacturers instructions shall be followed.
a) An adequate, uninterniptible power supply shall be used.
b) Depending on the measuring system employed, a torsion-resistant stand or sufficiently rugged attachment (wind load!) of the optical components shall be ensured. Particularly when using long measurement paths on systems devoid of automatic adjustment features, a sufficient long-term stability of the measured signal has to be guaranteed. In the case of pronounced ambient air temperature variations or changes in the solar radiation, the dc-adjustment (change of alignment) caused by thermal effects needs to be taken into account.
C) Compliance with the operating conditions defined by the manufacturer (thermal requirements) for both the analyser unit and optical system components shal be ensured. On DOAS measuring systems combining the receiver and analyser unit in a single assembly, meeting these criteria may call for additional measures since the entire system is exposed to ambient conditions. If the optical components and the analyser unit are installed separately, appropriate steps shall be taken (e.g. air conditioning systems, heaters) to guarantee that the manufacturer-specified operating conditions (thermal requirements) will be met. particularly for the spectrometer unit. To optknise the systems availability, all optical components shall be protected against moisture effects (e.g. dew, precipitation).
d) The adjustment of a monitoring path is started by focussing the radiation source on the recefver% optical system (or. in the case of monoslatic systems, on the ratio-reflector or mirror element used). The size of the focus poinr shall be selected such that minor 5ystem dc-adjustments (e.g. due to thermal effects) will not necessarily result in a total signal loss but can be tolerated (typically between 0.5 m to 2 m). These settings will be dependent on the selected monitoring path length and the size of the receivei’s optical system; they shall be re-set during every new installation with a view to maximising the signal level.
e) For some systems adjustments shall preferably be carned out in the dark or in half-light (twlght) cxmdltions since the visible spectral portion of the emitting light source Is helpful when adjusting focus settings, optical transfer devices. etc.
NOTE New optical monostabc setups (71 do not requre an aiustment at night They are also simple to aust at day5ght. The acuslment of the lil beam and focal point does not require the visibility of the emitting bght.
f) Fibres for the deep UV range (solansatlon slabilised) shod be used. It working with light sources emitting below 280 nm, to avoid degradation of light transmittance.
g) If ozone-producing radiation sources are employed, suitable steps shall be taken (e.g. ventilation) to prevent any effects on the measurement and direct exposure to people.
h) Whenever the system le installed from scratch, its wavelength accuracy shall be re-checked. This can be done, for instance, with the aid of a mercury vapour spectral lamp.
I) A functional check of the DOAS measuring system shall be carried out before measurements are begun.
j) Beam alignment and blocking or optical path deflection systems may be necessary, especially for automatic operation. These systems shall be controlled as appropriate.
k) Once the monitoring path is set up and the optical adjustments have been made, all parameters of the DOAS measuring system which have been set or achieved for this speafic monitoring path shall be duly documented so that any dnft or dc-adjustments can be Identified. Where different monitoring paths are used,all parameters shall be documented for each monitoring path used. These data will include the following.