Replacing the TCD Filaments
A. StandardTCDdetectorblockaccess
1. Withasmallbladescrewdriver, free thefilament leadsfrom thebridge terminalby loosening the
setscrews.
2. Remove thedetectorassemblycover byunscrewing the thumbscrew thensliding thecoveroff
toward theright-handedgeof theGC;gentlyremove thewhite insulation toreveal thedetectorblock.
3. Disconnect thedetectorblockgas inletsandoutlets. Thereferencegas inlet isdisconnectedat the
polishingfilter immediatelybehind thecolumnoven. Thereferencegasoutlet isdisconnected inside
thecolumnoven. Disconnect thesamplegas inletat the fittingon thecolumn. Thedetectorblock
samplegas inlet tubinghasacoppersheathfor identification. Thesamplegasoutlet isusuallyrouted
out therightsideof thecolumnoven.
Exploded viewof the standardTCDdetector assembly
SRITCDdetectorsaremade to lasta long timewithouteverreplacing thefilaments. However,anyTCD
filamentsthatfailthediagnosticohmetertestmentionedpreviouslywillhavetobereplaced. Whiletheyshare
thesameouterassembly, thereareafewdifferencesbetween thehigh temperatureTCDdetectorblockand
thestandardTCDblock. Bothdesignsarediscussed. Allfilamentsarefragile;handle themwithcare. Have
colored inkpens,electrical tape,whateveryouwilluseforcolorcodingcloseathandbeforeyoubegin. It is
besttogoslowly,color-codingthenreplacingeachfilamentoneatatime. IFYOUMIXUPTHEFILAMENT
LEADS,YOURTCDWILLNOTWORK!
DETECTORS
Thermal Conductivity Detector - TCD
