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. 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
Specifications
General features
| Measurement technology: | Innovative NDIR Sensor (non-dispersive infrared sensor) |
| Detectable gases: | CO2 CO N2O CH4 CnHm* CF4 SF6 H2O |
| 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 |
| 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 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 (option) – incl. data transmission cable 1 m |
| Analogue voltage output (option): | 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 Measurement Ranges
Measuring ranges / Full scale value (F.S.) 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 CO2 CO N2O CH4 CnHm* CF4 SF6 H2O Measurement ranges on request
Infrared module NDIR Ultraviolet module NDUV Ultraviolet module NDUV / UVRAS
* Calibration with Propane
Table of Detection Limits (= 3 σ) in Percent of Full Scale
Detection Limits / % of Full Scale Value (F.S.) 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 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% CH4 < 0,1% < 0,1% < 0,1% < 0,1% < 0,1% < 0,1% < 0,1% < 0,3% < 0,5% CnHm* < 0,1% < 0,1% < 0,1% < 0,2% < 0,2% < 0,2% < 0,2% < 0,5% < 0,5% CF4 < 0,2% < 0,2% < 0,2% SF6 < 0,1% < 0,1% < 0,1% < 0,2% < 0,5% < 0,3% < 0,3% H2O Measurement ranges on request
Infrared module NDIR Ultraviolet module NDUV Ultraviolet module NDUV / UVRAS
* Calibration with Propane
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: