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© TDL Sensors Ltd 2012
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
High sensitivity (ppb, ppm concentrations)
Interference free gas measurements
Large dynamic range
Absolute measurements– no drift, no calibration, inherently linear
Real-time (10 Hz or faster response)
Very low maintenance
Advantages of laser based gas analysers:
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
It’s a high-resolution spectroscopic measurement
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
Tunable Laser Gas Monitoring
Mid IRNear IRUV-Vis Visible
© TDL Sensors Ltd 2012
0.7-2.7 µm
Laser diodes, VCSELs
3-5 µm 4.2->12 µm
DFGs
QCLs
Tunable Laser Gas Monitoring
We use the IR spectral region for gas measurements
Tunable lasers available within this region
© TDL Sensors Ltd 2012
Tunable Laser Gas Monitoring
NIR Mid-IR
Each gas absorbs light in a characteristic way.
Hydrogen Fluoride (HF)Carbon Dioxide (CO2)Nitric Oxide (NO)Ammonia (NH3)Carbon Monoxide (CO)Methane (CH4)Water (H2O)
This means that each gas has a unique spectrum or “fingerprint”.
© TDL Sensors Ltd 2012
Tunable Laser Gas Monitoring
Tunablelaser
PhotodetectorI0
Beer - Lambert Law:
LI
IT )(exp)(
0
Absorption coefficient PathlengthTransmission
II0
Laser frequency tuned
I
Transm
ission
Signal out
GasGas
Gas in Gas out
Measurement cell
L
© TDL Sensors Ltd 2012
Low resolution
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
Low resolution
Difficult todistinguishbetween the twospecies
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
High resolution
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
High resolution
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
High resolution
Individualabsorption linescan be resolvedfree from interference
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
High resolution
Laser tunes overa narrow range
Tunable Laser Gas Monitoring
© TDL Sensors Ltd 2012
Technology
Real-time measurements
– Laser wavelength is tuned across absorption feature at >1 kHz and then averaged
– Concentration reported at rates as high as 10 Hz
© TDL Sensors Ltd 2012
Technology
Gas Performance option
Range Detection limit Measurementrate (Hz)
CO PlusStandard
0 – 20 ppm0 – 200ppm
2 ppb0.1 ppm
1010
HCl PlusStandard
0 – 10 ppm
0 – 500 ppm
5 ppb0.5 ppm
1010
HF PlusStandard
0 – 10 ppm0 – 100 ppm
2 ppb0.01 ppm
1010
NO PlusStandard
0-20 ppm0-2000 ppm
5 ppb1 ppm
1010
NH3Plus
Standard0 – 2 ppm
0 – 200 ppm2 ppb
0.1 ppm10
10
NO2Plus
Standard0 – 2000 ppm
–1 ppm
–10
10
SO2Plus
Standard–
0 – 500 ppm–
1 ppm10
10
O2Plus
Standard0 – 2 %
0 – 25 %20 ppm
0.05 %10
10
CH4Plus
Standard0 – 2 ppm
0 – 1000 ppm1 ppb
0.5 ppm10
10
N2O PlusStandard
0 – 20 ppm–
2 ppb–
10-
H2S PlusStandard
0 – 500 ppm–
1 ppm–
0.1–
HCN PlusStandard
0 – 10 ppm0 – 100 ppm
5 ppb0.1 ppm
1–
CO2Plus
Standard0 – 2 ppm
0 – 1000 ppm1 ppb
0.5 ppm10
10
Typical gasesand specification
© TDL Sensors Ltd 2012
Technology
Tunable laser control& data acquisition
electronicsTunable laser
& photodetector
Mechanicaldesign
Software &firmware
Signalprocessor
Spectroscopy
Core system components
© TDL Sensors Ltd 2012
Technology
High sensitivity
Interference free gas measurements
Absolute measurements– No drift, no calibration, inherently linear
Real-time (1 s response)
In-situ and non-invasive (optical technique)
Very low maintenance
Summary:
© TDL Sensors Ltd 2012
Technology
ContactTDL Sensors Ltd
The Incubator Building48 Grafton Street
Manchester M13 9XXUnited Kingdom
Tel: +44 (0)161 606 [email protected]
www.tdlsensors.co.uk
![Heterodyne frequency measurements with a tunable diode ...between TDL [near P(41) of the OCS molecule] and the P(36) line of the COz laser. The TDL current was about -0.69 A, just](https://img.dokumen.tips/doc/110x75/60a9a79f191cc1181e2a017d/heterodyne-frequency-measurements-with-a-tunable-diode-between-tdl-near-p41.jpg)
