Honeywell XNX - 3�2�8 Zero And Span Calibration For Mpd Sensors

XNX Universal Transmitter
Section 3 - Calibration
97
3.2.8 Zero and Span Calibration for MPD Sensors
Caution: Extendedorfrequentexposuretoelevatedconcentrations
ofcombustiblegasesmayaffectsensorsensitivity.Verifysensor
performancebyfrequentcalibration.
Caution: Beforeinitialcalibrationallowthesensortostabilizefor30minutes
afterapplyingpower.Wheninzeroandspancalibrationmodes,thecurrent
outputfromthesensorisinhibited(default2mA)toavoidfalsealarms.
TheGasCalibrationmenuisforbothzeroandspancalibrations�
ThissectiondescribeshowtocalibrateMPDammablesensors
ttedtothetransmitter�Thecalibrationadjustmentsaremadeon
thetransmittersdisplay�Gassingisperformedatthesensor,
whichmaybelocallyorremotelylocated�
Thefollowingequipmentisrequired:
• Flowhousing(P/N:1226A0411)
• Testgas
• Regulator
Note:ZerogasandSpangasshouldbeataboutthesamehumiditylevelsto
avoiderroneouscellresponses.
1�AttheMPD,removetheweatherproofcap,ifequipped�
2�FittheowhousingontotheMPD�
Figure 214. Flow Housing
3�Reversethecapremovalprocedure�Figure215showsthe
owhousingaccessoryttedtotheMPD�
Figure 215. MPD with Flow Housing
4� Connecttheowhousing(usingeithergaspipe)tothe
regulatedcylindercontainingaknownconcentrationofthe
targetgasatapproximatelythesensoralarmpoint,e�g�,50%
LELmethaneinair�
Warning: Assometestgasesarehazardous,exhausttheflowhousingoutlet
toasafearea.
5�FollowtheprocedureinSection3�2�1forbothzeroand
spancalibrations�
6�Applythetargetgastothesensor�Passthegasthrough
theowhousingatarateof 300-375ml/minforXNXEC
sensorsor500±200ml/minforXNXmVsensors �