Owner's manual

<2 INTRODUCTION AND GENERAL DESCRIPTION> 2-1
IM 11Y01B02-01E-A 4th Edition September 11, 2012-00
2 Introduction and General Description
TheTDLS220TDLanalyzerisdesignedtomeasureconcentrationsofselectedtargetchemicalspecies
(mostoftenOxygenorMoisture)ingasphasesamplesthathavebeenextractedfromtheprocess.
Typically,thereisacontinuousowofanalyzedgasthroughtheTDLS220opticalgascell.Thegas
shouldbepre-conditionedtomeetthesampleinletrequirementsincluding(butnotlimitedto)particulate
removal,dewpointcontrol(heated),owandpressurecontrol,etc.Chemicalcompositionofthesampled
gas mixture is determined by the end user. It is the end user responsibility to ensure safe delivery of the
sampled gas to the analyzer and the subsequent return of the gas to the process or its utilization after
analysis.
Theanalyzermeasureschemicalconcentrationsonapathaveragedbasis.Unlesstheextractivesampling
systemup-streamremoveswater(orothercondensables)then,themeasurementsareconsideredtobeon
a‘WetBasis’.
Measurementsarepossible(withcorrectanalyzerconguration)atthefollowingconditions:
 •Gastemperaturesupto120˚C(248˚F)
 •Gaspressuresupto4BarG(75psig)
Each application may differ in maximum limitations depending upon the combination of gas temperature,
gas pressure, and concentration of the gas being measured.
ThestandardanalyzerisdesignedforoperationinaSafeArea(GeneralPurpose).TheadditionofaPurge
System facilitates operation in Hazardous Areas.
ThebasicTDLS220analyzercomprisesamountingpanelwiththreeunitsattached,theControllerhousing,
thePowerSupply/HeatingenclosureandFlowCell(oroptionalheatedowcell).
Several options may be added to the standard analyzer such as:
 •MiniDisplay(4line,20character)or6.5”screenandkeypad
 •RemoteInterfaceUnit(notrequiredfornormaloperation)
 •InsulatedandHeatedowcell
 •HazardousAreapurgesystems
 •Otheroptionsmayalsobeadded
2.1 Functional Description
TunableDiodeLaser(orTDL)measurementsarebasedonabsorptionspectroscopy.TheTDLS220
AnalyzerisaTDLsystemandoperatesbymeasuringtheamountoflaserlightthatisabsorbed(lost)as
it travels through the gas being measured. In the simplest form a TDL analyzer consists of a laser that
produces infrared light, optical lenses to focus the laser light through the gas to be measured onto a mirror
and back through the gas and then on to a detector, the detector, and electronics that control the laser and
translate the detector signal into a signal representing the gas concentration.
Gasmoleculesabsorblightatspeciccolors,calledabsorptionlines.ThisabsorptionfollowsBeer’s
Law.
UsingaTunableDiodeLaserasalightsourceforspectroscopyhasthefollowingbenets:
 •Sensitivity.Aslowas10
-6
by volume, lower with pathlength enhancement.
 •Selectivity. The narrow line width of the laser is able to resolve single absorption lines.
This provides more choices of a particular peak to use for measurement, usually allowing
one isolated peak to be used.
 •Power.Diodelasershavepowerrangingfrom0.5mWto20mW.
 •Monochromatic,nodispersiveelement(lter,etc.)required.Lightsourceitselfisselective.
 •Tunable.Wavelengthcanbesweptacrosstheentireabsorptionfeature,whichallows
 resonant(peak)andnonresonant(baseline)measurementduringeveryscan.