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Model RI-85 is based of NDIR method (Non-dispersive Infrared) and this structure is shown
below.
The infrared beam emitted from the light source passes through the measuring cell, and optical
band pass filter which can pass the absorption wave of measuring gas and attains to the
infrared sensor. The amount of infrared attaining to the infrared sensor through measuring
cell is absorbed by the measuring gas when measuring gas is supplied into the measuring cell
and will decrease according to its concentration. The variable amount of infrared is measured
by the infrared sensor and it is displayed as gas concentration.
Then, there is no sensitivity against other gases which have the different absorption wave from
the measuring gas. And, there is no sensitivity against N2 and H2 etc which cannot absorb
infrared. There is not poisoning material to be absorbed and almost no sensitivity drop on this
detection principle.
9．Detection principle
∫
Measuring gas
Measuring cell
Infrared
sensor
Ｓ
Band-pass
filter
Amp.
Light source
