
Model B12-69WetOxidantGasTransmitter
O&M Manual-15 -
Rev-G, 7/15
CALIBRATION
Transmittercalibration requiresadjustment ofboth zeroand span. Zeroisadjusted when the
sensorisexposedtoaircontaining nooxidantgases.Spanisadjustedwhenagasstreamcontaininga
known concentrationofoxidant gasispassed through the lowvolume flowcell.
ZEROADJUSTMENT
Aspreviouslymentioned, adjusting thetransmitterzerorequiresthat the sensorbe exposed to
oxidant gasfree air.The simplestapproachistosimplyexposethesensortoambient airthat isfree of
gasesto whichthesensorwillrespond. Threading thelowvolumeflowcell onto the sensorwill isolate the
sensorfromsurrounding airforzeroing purposes.
Ifthe areainwhichthe sensorisoperatingisknownto begasfree, thenthetransmittercan be
zeroedwithout furtherequipment. Ifnot, useof“zeroair” fromagascylinderisrecommended. Zeroair
isavailableaspartofallATIcalibration kits,ormaybeobtained fromanyspecialtygassupplier.When
zeroairisto beused, alowvolumeflowcell(partno.00-0422)mustbe used. The lowvolumeflowcell
providesaconfinedspacearoundthesensorintowhichthezeroaircanflow. The flowcellsprovide tube
fittingsat the bottomto connect airtubing asshown inFigure2.
Tozerothetransmitter,removethe coverandconnectaDVMtothe testpointsshowninFigure
6. Observethe DVMvalueto be surethat itisnolongerdeclining, andthat itisstable±4mv.Usethe
zeropotentiometer(Figure6)to adjustthe testpoint voltage to0.040 VDC (40mv.).Ifthe transmitteris
supplied with the LCD option, noDVM isrequired.
SPANADJUSTMENT
Oncethezerohasbeenset, slidethelowvolumeflowcellonto thesensor(ifitisnotalready
there fromzeroing). Attacha source ofgaswith aknow chlorinegasconcentration andadjust the sample
flowrateto 500 cc/min. Atypicalchlorine gassourceisthe electrochemicalchlorinegenerator
manufactured byAdvanced Calibration Designsin Tucson, AZ.Allowsample to flowfor10 minutes.
ObservetheDVMvalue. The reading shouldbe relativelystable±4mv.Adjustthe span
potentiometer(Figure6)untilthe propertestpoint voltageisobtained. The propervoltage to set when
adjustingtransmitterspanwillvarydepending on therangeofthetransmitter.The following formulais
used tocalculatetheproperspan voltage foranytransmitter.
V = 0.040 V + [0.160X (Measured Concentration ÷Transmitter Range)]
Asanexample,supposeyou arecalibrating atransmitterwitharangeof0-10 PPM,andthe
chlorine gasstandard used forcalibrationhasavalue of5 PPM. The above formulawould thenbecome:
V = 0.040 V + [0.160X (5 ÷10)] = 0.120V.
Therefore, adjusting the transmitterto areading of120 mv.at the testpoint wouldproperly
calibrate the transmitter.
NOTE: The responseofawet gassensoris1:1forchlorine,bromine, oriodine.Thechlorine dioxide
responseisapproximately0.7:1, meaningthat thegasstandardvalueinthe aboveequationmust
be multiplied by1.4 to arrive at the correct calibration value.