Laser Diode Gas SensorsPhotonic SensorsSwiss Laser Net Workshop Biel 17.09.09

Thomas Hessler

Overview

Leister and ist photonic activities

TDLS detection principle

TDLS product plattform

Applications

PLASTIC WELDING PROCESS HEAT LASERSYSTEMS MICROSYSTEMS

LEISTER Process Technologies

LEISTER Corporate

Production,Logistics

Corporate HeadquarterMarketing & Sales,Administration,Corporate R&D

Axetris,Production

Sarnen, CHKägiswil, CHKägiswil, CH

Corporate Sites

Photonic Sensor Activities at Axetris

Laser Gas SensorsTunable Diode Laser Gas Sensors

IR SourcesBroad band thermal IR emitters for NDIR gas sensors

Micro-OpticsRefractives and diffractives for opticalsensors

p. 6

Reference

GasVolume

Detector

IR Source

Technology - TDLS Measurement Principle

Laser diode scan acrosssingle gas absorption line.

Laser Scan

Laser line

Gas absorption lines

λ

A

λ

A

GasVolume

Laser

Laser signal information:Laser intensity & wavelengthvary linearly with drive current

Gas absorption signal:The detector sees less intensityas the laser hits the gas line

Optical system & reference information: On modulation frequency f

Gas concentration signal:On modulation frequency 2f

I

I

t

t

No gas

With gas

f

2f

λ

λ

Intrinsic reference channelHigh linearity

Laser signal information

Laser Scan

Gasabsorption information

λ

A

Technology - TDLS Measurement Principle

Technology – 1st or 2nd Order

Optical and optoelectronic components (laser & detector) increase significantly in price with wavelength (if available)=> work at 1st or 2nd overtone

Abs

orpt

ion

Wavelength (µm)

4.262.041.57

FundamentalAbsorption Band Envelope1st

Overtone

2nd

Overtone

CO2

1,57 1,571 1,572 1,573 1,574 1,575

COCO

2

Abs

orpt

ion

(a.U

.)

Wavelength

TDLS - Selectivity

TDLS is a high resolutionmeasurementSuperposed bands can beresolved for each gas: Results in high selectivityExample CO2/CO: Envelopes overlap, single absorption lines do not

TDLS - Good for small molecules

TDLS can measure gases with resolved rotation & vibration bands, i.e. gases with small molecules.E.g. alkanes: Ok for CH4, C2H6, but not for longer chains

Electronics

Laser Diode

Mirror

Photo Diode Gas Volume

Technology - Laser Gas Monitor

Sharp laser linehigh selectivity

Intrinsic reference channelhigh, long term stability, calibration-freecontinuous status monitoring

Optical technologycontactless & hot gas measurement

Business Focus

Laser gas detectionPresent Focus on NH3, CH4, CO2, O2Flow through and diffusive set-upsSelf-contained OEM modules, sub-mounts

Applications inProcess control & environmental monitoringIndustrial safety Climate & air conditioningMedical technology

IR Microsystems provides:Self-contained measurementsystem with integrated optics(probe or flow-cell)Digital or analog data output

Customer provides:Input Power (10-30 V)Conditioned/filtered gasPurge gas (where necessary)

Measurementinterface to customer:

TDLS Gas Monitor Set-up

Diffusive: LGD P50 Single point

Flow: LGD F200 (H) Ambient / heated

Technology (Flow) - LGD F 200 (H)

Flow-through cellOptional heating up to 190°CModular design

System Specifications

below detection limitDriftdepending on gas & applic. ppm- or %-rangesMeasurement rangedepending on gas & applic.modular, different path lengthsMeasurement cell layout

ambient, optional up to 190°CMeas. temp. flow-throughflow-throughLGD F200H layout

800 ppm130 ppmOxygenO2

30 ppm5 ppmCarbon DioxideCO2

3 ppm0.5 ppmMethaneCH4

2 ppm0.3 ppmAmmoniaNH3

Peak-to-peak noiseat T: -40°C to +65°C

Precisionat T constantMain Target Gases

LGD F 200 (H) - Specifications

~Compact multigas

~~Acquisition cost

TDLS

~

E-Chem

Calibration-free~~High Stability~~High Selectivity

~Overload damage or ageing

Fast Recovery time

Rugged~~Low cost-over-time

Non-contact measurementCont. Sensor status monitoring

Paramag.NDIR

Characteristics

Gas Sensing Technologies

Selected ApplicationsNH3

SCR / Emission Control

Safety / Refrigeration

Livestock Climate Control

CH4

Environmental Monitoring / Landfill

SCR system monitoring, combustion processes inpower plants, powerstations, diesel engine development

Need to measure NH3 hot (190°C) to 1ppm(acid dew point, water)

LGD F200 H offers real time emission controlwith non-contact measurement in heated sample cell

0.3 ppm2 ppm

Precision at T = const.:Peak-Peak Noise -40°C – 65°C:

SelectivityNon-contact

Main application specific USP

SCR Process Monitoring

Emission Control

0

1

2

3

4

5

6

7

8

9

10

11

12

500 1000 1500 2000 2500

Time [s]

Set 7 ppm

Set 8 ppm

Set 9ppm

Set 10 ppm

Set 0 ppm

Set 2 ppm

Set 6 ppm

Set 5 ppm

LGD F200 NH3 - measurements

resolution

LGD F200 NH3 - measurements

linearity reproducibility

LGD F200 NH3 - measurements

Workplace and site safety monitoring: 1-100 ppmCurrent sensors:

Life time ~ 12 months, 6-months calibration cycleHigh cost for end-userNo sensor status monitoringCross sensitivities / false alarms

microLGD offers better performance at lowercost-over-time

Plant & personnel safety monitoring

0.3 ppm2 ppm

Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:

Selectivity ReliabilityCost-over-time

Main application specific USP

Safety / Refrigeration

Monitor NH3 to improve health and growth of livestockScrubb NH3 out of exhaust air for environmental protection

Well-suited sensors are not available today

Current sensors:Life time shortened to days by NH3 backgroundCross sensitivities

microLGD enables livestock applications

Ventilation Control & Ammonia Scrubbing

0.3 ppm2 ppm

Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:

Life-timeCost-over-time

Main application specific USP

Livestock Climate Control

0.3 ppm3 ppm

Precision at T = const.:Peak-to-Peak Noise -40°C – 65°C:

SelectiveHigh dynam. range

Main application specific USP

Landfill / waste water gas monitoring

Monitoring of waste water for CH4emission; landfill de-gasing (safety)

LGD F200 offers real time,monitoring with high dynamic range

Selective measurement of methane

0

2

4

6

8

10

12

14

0 500 1000 1500C

H4 [p

pm]

Time [s]

5 ppm

6 ppm6.9 ppm

7.9 ppm

10 ppm

3.9 ppm

2 ppm

0 ppm

Environmental Monitoring

Summary

The optical, non-contact measurement principle and the intrinsic reference channel and the high selectivity offer significant benefit in a wide range of applications. TDLS moves from high end to upper medium end applications, component cost hinder further penetration into mainstream applications.Leister offers self-contained laser gas monitoring systems to OEMs to use the benefits of this technology in their field of activity.

Thank you for your attention!