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MultiGas NDIR 红外模块



Gas analysis based on the NDIR technique is an established method to determine the concentrations of gases in complex mixtures. The RITTER »MultiGas« sensors use new optical components for optimal analysis results: Up to 3 optical filters analyse the gas which flows through the sensor as one gas stream. The optional oxygen, pressure, and humidity sensors are in-line with the same single gas stream.

The individual internal modules are sealed by means of O-ring connections.

In order to achieve an optimum adaptation to the required measuring range, the lengths of the modular measurement cells (= cuvettes) can be implemented in the range of 5 mm (large measurement range in percentage level) up to 250 mm (small measurement range in ppm level).

Cuvettes with a length ≥ 20 mm are coated with a resistant gold layer in order to improve the reflection properties for low concentration level detection. Cuvettes used with aggressive gases are gold-coated as well.

The other internal mechanical parts are made out of aluminium, optionally out of stainless steel.

For fast response applications the measuring system delivers a stable result within t90 ≈ 3 seconds.

The entire unit can be disassembled for easy maintenance/service.


  • Biogas / natural gas analysis
  • Environmental and Process Measurement
  • TOC analysers
  • Continuous Emission Monitoring (CEM)
  • Elemental analysis
  • Industrial gas analysis


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General features

Measurement technology: Innovative NDIR Sensor (non-dispersive infrared sensor)
Detectable gases:
Number of simultaneously detectable gases: max. 3 per sensor unit
Measurement ranges: See below
Flow rate range: 5 ~ 300 ltr/h – For higher flow rates the sensor can be operated in bypass
Max. gas inlet pressure: 300 mbar
Pressure loss (without additional optional sensors): 10 @ 100 / 35 @ 200 / 70 @ 300 (mbar @ ltr/h)
Temperature compensation: Yes
Data acquisition software: Yes
Lifetime of IR radiation source: > 40 000 h
Measurement cuvette: Aluminium, with measurement ranges ≤1% gold-plated inside
Cuvette sealing: Viton O-ring
套管: High-quality table-top casing, aluminium
Dimensions (W x H x L): 171 x 86 x 290 mm
重量: approx. 2 kg
Gas connections: PVDF screw-type tube connection for tube Øi 4mm, Øo 6 mm

Measuring response

Linearity error: < ± 1% F.S.
Repeatability: ± 0.5% F.S.
Long term stability zero: < ± 2% F.S. / week
Long term stability span: < ± 2% F.S. / month
Temperature influence of zero point: < 1% F.S. / 10K
Temperature influence of span: < 2% F.S. / 10K
Cross sensitivity: < 2% F.S.
Pressure influence: < 1.5% / 10hPa of reading
Warm-up time: 2 min
Response time (t90): ≈ 3 sec
Sampling frequency by software: ≤ 10 Hz
Detection limit: See below
Resolution: 0.5 x detection limit
Water vapour: No influence with measurements of CO2 and CH4

Electrical features

Power supply: 24 VDC incl. power plug 100 ~ 240 VAC / 24 VDC
Average power consumption: < 1W
Interface: USB (standard), RS232 (选项) – incl. data transmission cable 1 m
Analogue voltage output (选项): 0-2V / 0-5V / 0-10V

Climatic conditions

Operating temperature: +15 ~ +45 °C
Storage temperature: –20 ~ +60 °C
Operating pressure: 800 ~ 1200 hPa (mbar)
Ambient humidity: 0 ~ 95% rel. humidity // Condensing inside of sensor must be prevented!

Analysis of CnHm*

The calibration of sensors for CnHm will be performed with propane. Aromatic hydrocarbons are also measured but with a different weighting. This means that the sensitivity of the sensor is significantly smaller with these gases than with other hydrocarbons.


Table of Detection Limits (= 3 σ) in Percent of Full Scale


The following recalibration intervals are recommended for IR sensors:

  • Zero-point: Weekly with inert gas, e.g. Nitrogen
    The recalibration of the zero point is described in the software manual.
  • End-point (full scale): Every 3 months with suitable calibration gas