General Operating Procedures
2. The approximate pressures required for the correct
hydrogenandairflowsare labeledon theright-handsideof
the GC chassis under “GAS FLOW RATES.” Set the
hydrogenflowto3mL/minuteandtheairflowto100mL/minute
using the trimpotson the topedgeof theGC’s frontcontrol
panel. To adjust a pressure setting, hold down the
SETPOINTbuttonwhile turning thecorresponding trimpot
until youcan read thedesiredpressure setting in theLED
display(makesure theLED“DISPLAYSELECT”switch is
on“ALLBUTTONS”).
1. Set theNPDamplifiergainswitch toHIGHformostapplications.
4. Set theNPDbead current to -360. Higher current settingsmaybeused, but the life and subsequent
sensitivityof theNPDbeadwillbereduced.
3. Set theNPDdetector temperature to250
o
C:holddown theSETPOINTbuttonwhile turning thedetector
heat trimpotuntil thedesiredsetpoint isvisible in theLEDdisplay.
5. Press theACTUALbutton toobserve the temperatureof theNPD in theLEDdisplay. When thedetector
has reached theset temperatureand thesignalappearsstable, theNPD is ready foruse.
NPD/DELCDCombination Detector
NPDDetector
1. Set theDELCDamplifiergainswitch toLOW,and the
NPDgain toHIGH.
2. Set theNPD/DELCDhydrogen to3mL/minuteand the
airto100mL/minusingthecorrelatingpressurelabeledon
theright-handsideof theGC.
ExampleGasFlowRates table: thisparticularGC
isequippedwithNPD/DELCDandFIDdetectors.
3. Set theNPD/DELCDdetectorheat to150
o
C.
4. Set the DELCD reactor temeprature to 260. The
number260 represents1000
o
C; theDELCDwillheat to
about 254 and stabilize. Thevisible endof the reactor
tubewillglowbrightredwiththehightemperature.
5. Inject samplewhen thecombinationdetectorhas reached theset temperaturesand theirsignalsappear
stable.
Note:
MostSRINPDsare installedonaGCwithoneormoreotherdetectors. Therefore,SRI tests itsNPD
detectorswithheliumcarriergas.
DETECTORS
Nitrogen/Phophorus Detector - NPD
