RITTER »MultiGas« Infrared Modules NDIR

Table of Contents

Description

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 and offer additional protection against slightly corrosive gases. 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.

Applications

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

Specifications

General features
Measurement technology:Innovative NDIR Sensor (non-dispersive infrared sensor)
Detectable gases:
CO2 CO N2O CnHm CH4 CF4 SF6 H2O
Number of simultaneously detectable gases:max. 3 per sensor unit
Measurement ranges:See Table of Measurement Ranges
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
Casing:High-quality table-top casing, aluminium
Dimensions (W x H x L):171 x 86 x 290 mm
Weight:approx. 2 kg
Gas connections:PVDF screw-type tube connection for tube Øi 4 mm, Øo 6 mm
Measurement data
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 Table of Detection Limits
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
50/60 Hz: 24 VDC
Average power consumption: < 1W
Interface: USB (standard), RS232 / CANbus / CANopen (options)
incl. data transmission cable 1 m
Analogue voltage output (option): 0 – 2 V / 0 – 5 V / 0 – 10 V
Gas parameters
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.

List of standard measurement ranges *1 ( and detection limits *2 )

Standard Measuring Ranges with respective Detection Limits ( % of F.S. *3 )
100
Vol.%
50
Vol.%
30
Vol.%
20
Vol.%
10
Vol.%
5
Vol.%
1
Vol.%
5,000
ppm
2,000
ppm
1,000
ppm
500
ppm
300
ppm
100
ppm
50
ppm
10
ppm
1
ppm
CO2
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.3%)

(< 0.3%)
CO
(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.3%)

(< 0.5%)

(< 0.5%)
N2O
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.3%)
CnHm*4
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.5%)

(< 0.5%)
CH4
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.3%)

(< 0.5%)
CF4
(< 0.2%)

(< 0.2%)

(< 0.2%)

(< 0.02%)

(< 0.05%)
SF6
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.2%)

(< 0.5%)

(< 0.3%)

(< 0.3%)
H2O
*1 A standard measurement range is defined by / *2  (= 3 σ) in Percent of Full Scale / *3 F.S. = Full Scale / *4 Calibration with Propane

Infrared module NDIR Ultraviolet module NDUV

Definition of Detection Limit

The Detection Limit is the smallest measurement value which can be obtained with a specific uncertainty. This uncertainty includes the resolution, noise and stability of the gas sensor for a specific gas and specific measurement range. For evaluation of the detection limit value, several single measurements are taken at the identical measurement conditions. With the obtained single measurement results the standard deviation “Sigma” (σ) is calculated. The values given in the table equal the triple amount of Sigma.

Recalibrations

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

V 1.0 / Rev. 2024-02-07 / Subject to alterations.