Serinus 40 User Manual 2.2
1.3 Nomenclature
NO: Nitrogen oxide, or nitric oxide.
NO
2
: Nitrogen dioxide.
NO
x
: A generic term for mono-nitrogen oxides NO and NO
2
.
Span: A gas sample of known composition and concentration used to
calibrate/check the upper range of the instrument (GPT using NO gas).
Zero: Zero calibration uses zero air (NO
X
scrubbed ambient air) to calibrate/check
the lower range of the instrument.
Background Cycle: Removes unwanted signal from the measurement signal. This is
accomplished by pre-reacting the sample gas with ozone outside the
measurement cell. The pre-reacted gas is then fed into the cell where this
signal is stored as the background signal. This background measurement is
then used to correct the sample measurement by subtracting the
background signal from the measurement signal. Background cycle can be
described as a dynamic zero where unwanted signals generated from the
photomultiplier tube (detector) due to internal offsets (dark current) or
unwanted cell luminescences are removed.
Zero Drift: The changes in instrument response to zero pollutant concentration over
time.
Zero Air: Is purified air in which the concentration of NO is <0.5 ppb and NO
2
is <0.5
ppb with water vapour of less than 10% RH. Sufficient purified air can be
obtained by passing dry ambient air through an activated charcoal filter, a
purafil cartridge and a particulate filter.
External Span Source: Span gas that is delivered via an external accredited cylinder containing NO in
balance with N
2
(e.g. NATA/NIST).
Sample Air: Sample air is defined as the sample before it has entered the reaction cell, as
distinguished from the exhaust air.
Exhaust Air: Exhaust air is the sample air after it has passed through the
reaction/measurement/detection cell and is moving towards being expelled
from the analyser.
ID and OD: These are measurements of tubing, ID is the internal diameter of tubing, and
OD is the outer diameter.
Multi-drop: A configuration of multiple analysers connected via the same RS232 cable.
Photomultiplier Tube: A highly sensitive device which can detect extremely low levels of light
(photons) and multiply the electrical signal to a point where it can be
accurately measured. These are often called PMTs for short.
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