GD-70D - 140 -
<NDIR (Non-Dispersive Infrared Absorption Type>
IR light enters the cell and gas absorbs the beam, so the absorption rate and the gas concentration will
correlate. The IR detector detects the IR light and will put it out as gas concentration.
The band pass filter only lets specific wavelength that is absorbed by the target gas. The detector will not
detect any light that has different wavelength. Also, the detector will not detect gas that does not absorb IR
rays.
Special precautions for this principle
1. The alarm must be set within a range where the performance of the detector can be ensured. The
standard alarm setpoint value are 50ppm(1st), 100ppm(2nd).
2. This is a safety unit, not a control unit.
The alarm contact output of the detector must be used for an external alarm lamp/buzzer, while the
analog signal output must be used for an indicator or external recorder. If these outputs are used to
control other units, we shall not be responsible for any malfunctions.
3. It is recommended that a regular maintenance and sensitivity calibration are performed for every six
months.
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