Float sensor

Float level sensors are continuous level sensors attributing a magnetic float that move up and down as liquid levels change. The movement of the float creates a magnetic field that actuates a hermetically sealed reed switch in the stem of the level sensor, triggering the switch to open or close.

1. FLOAT SENSOR

2. LEVEL SENSOR
YOUR SECTION SUBTITLE
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3. LEVEL MEASUREMENT
•Levelsensingdevicescanbedividedintofourcategories
•Directsensing,inwhichtheactuallevelismonitored
•Indirectsensing,inwhichapropertyoftheliquid,suchaspressure,is
sensedtodeterminetheliquidlevel
•Singlepointmeasurement,inwhichitisonlynecessarytodetectthe
presenceorabsenceofaliquidataspecificlevel
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4. SIMPLE SIGHT GLASSES
•Avisualindicationofthelevelcanbeobtainedwhenpartofthevesselis
constructedfromtransparentmaterialortheliquidinavesselisbypassed
throughatransparenttube.
•TheliquidlevelthencanbeobserveddirectlyinthesightglassGlassgaugesare
cheapbuteasilybroken,andshouldnotbeusedwithhazardousliquid.
•Theadvantageofusingstopvalveswiththeuseofabypasspipe,istheeasein
removalforcleaning.
•
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5. FLOAT SENSORS
•Therearetwotypesoffloatsshown:theangular
armandthepulley
•Theadvantagesofthefloatsensorarethatthey
arealmostindependentofthedensityoftheliquid
orsolidbeingmonitored,areaccurateandrobust,
andhavealinearoutputwithlevelheight.
•Oneofthesignificanttypesoffloatisamagnetrol
floatlevelswitchwhichconsistsofaplainfloatand
operatesviaamagneticcouplingaction.
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6. FLOAT SENSORS
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7. DISPLACER SWITCHES
•Inatypicaldisplacerswitchdesign,aspringisprovidedwhichis
burdenedwithweighteddisplacers.
•Thedisplacershavingweightsgreaterthantheprocessfluidgets
submergedintheliquidresultinginabuoyancyforcechange.
•Thiswillcauseavariationinthenetforceoperatingonthespring.
Ingeneral,thespringwillcompresswiththeraiseinbuoyancy
force.
•Justlikethefloatlevelswitches,amagneticsleeveandanon-
magneticbarriertubeisalsoincorporatedindisplacerswitches.
•Themagneticsleeveisattachedtothespringanditmoves
accordingtothespringmovementresultinginactivationof
switchingmechanism
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8. CONDUCTIVE PROBES
•Conductiveprobesareusedinsingleandmultiplepointmeasurementssystems.
•Lowvoltagesisappliedtotheelectrodesastheyareimmersedintheliquids.
•Theconductiveliquidcompletestheelectricalcircuitofthecontrol,which
activatesasemiconductorswitch.
•Theadvantageofconductiveprobesistheirlowcostandsimpledesign.
•Thedisadvantageisthattheyarelimitedtopointmeasurementandcanbeonly
usedwithconductiveliquids.
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9. CAPACITIVE PROBES
•Theyareusedforcontinuesmeasurements
•Thevalueofthecapacitancecanbechangebyvaryingthedielectric.
•Theprobeandthemetalwallofthetankformthetwoplatesofa
capacitor,andthecontentsinthetankisthedielectric.
•Whenthetankisemptythedielectricistheair.
•Asthelevelchangesthedielectricconstantchangesandcausesthe
capacitancechange.
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10. ULTRASONIC LEVEL SENSORS
•Ultrasonicorsonicdevicescanbeusedforsinglepointorcontinuouslevel
measurementofaliquidorasolid.
•Apulseofsonicwaves(approximately10kHz)orultrasonicwaves(morethan20
kHz)fromthetransmitterisreflectedfromthesurfaceoftheliquidtothe
receiver,andthetimefortheechotoreachthereceiverismeasured.
•Thetimedelaygivesthedistancefromthetransmitterandreceivertothesurface
oftheliquid,fromwhichtheliquidlevelcanbecalculated,knowingthevelocity
ofultrasonicwaves(approximately340m/s)
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11. RADAR MEASUREMENT
•Radargaugesdifferfromultrasonicinthattheyusemicrowaves
insteadofsoundwaves.
•Likeultrasonicdevicestheymeasurefromthetopofthevesselto
determinetheproductlevel.
•Twoexamplesofradargaugesarethe5.8GHzand24GHzsystems.
•Thehighertransmissionfrequencycanbeusedtodetectdry,non-
conductivematerialswithverylowbulkdensity.
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13. 10/18/2021 Float Sensor 13

14. B.Varun
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