OZONE ANALYZER BMT 965 Manual, Rev. 01/2024
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a) the flow rate of the sample gas,
b) the length of the tubing to the analyser,
c) the cross section of the tubing (we recommend tubing 3x5 mm, not more!),
d) the time lag of the analyser itself. At the recommended flow rate of 0.2 to 1.0 l/min time lag
will be 2 to 0.4 s with a 3x5 mm tubing length of 1 m.
Photometers and Dirt
Using 254 nm UV radiation the ozone
photometer "looks" through the gas, or
the water, in which the ozone is contained.
It looks via two cuvette windows made of
fused quartz. When these windows be-
come dirty the instrument cannot distin-
guish between a reduction of the UV radi-
ation by the ozone present in the cuvette -
and the reduction by dirty cuvette win-
dows. The most important rule for oper-
ating an ozone photometer is: "The only real enemy of an ozone photometer is dirt!"
When measuring ozone, namely in an industrial environment, it really pays off to thoroughly pro-
tect the ozone analyser from any dirt which might be contained in the ozone sample gas.
BMT ozone analysers for gaseous ozone are equipped with particle filters containing a replaceable
filter insert. The filter inserts should from time to time be checked for dirt (see page 52, Mainte-
nance), and be replaced on a regular basis depending on the degree of particle content of the sample
gas.
The ozone gas coming from most types of ozone generators contains more or less nitrogen oxides
because the oxygen feed gas contains nitrogen, inadvertently, or intentionally. Namely medium
sized and big generators are operated with high nitrogen doping. When such generators are serviced
without disconnecting the ozone analyser the danger of dirt getting into the analyser is particularly
high.
Caution: High concentration of nitrogen oxides in the sample gas must be avoided. If this could
occur e.g. during generator service, sample gas flow must be stopped!
The following two drawings show two possible configurations:
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