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MVI MANUAL
Ion Science Ltd
Page 7 of 23
Introduction
The Mercury Vapour Indicator (MVI) is primarily used to monitor environments where Mercury or any of the Mercury
compounds are produced, processed or stored and applications where Mercury vapours may pose a health hazard to
personnel.
Units of measurement used for detecting Mercury vapour are micrograms/cubic metre expressed as µg/m
3
.
The MVI has two manually switched ranges of measurement:
0-200 µg/m
3
with a resolution of 0.1 µg/m
3
0-2000 µg/m
3
with a resolution of 1 µg/m
3
Principle of Operation
A sample of the immediate atmosphere under investigation is drawn by the pump into a glass sampling cell where a
Ultra-Violet light source is absorbed by the sample. Photodiode detectors are used to measure the intensity of
radiation passing through the sample chamber. The optical system is designed specifically to detect Mercury in the
Ultra-Violet region of 254 nm.
The presence of Mercury vapour will reduce the radiation energy reaching the photodiode detector in proportion to
the vapour concentration. This change is then converted into an electrical signal and conditioned to provide a linear
reading on the front LCD as µg/m
3
.
An audible alarm is fitted which gives warnings when preset conditions are achieved.
