Instruction Manual

RevB MN301030 9of14
GETTINGSTARTED(continued) StepSix
Howtoselectthecorrectpressuretransmitter?
Theobjectiveistoselectasensorwithanoperationalrangethatwillcovertheentireapplicationspan.Ifthe
liquid height of the tank is above the sensor’s Maximum Liquid Height, then the sensor will  not be able to
read a full tank level.Compare the tank’s Pressure @ Full against the sensor’s pressure range to select a
sensor.
Tocalculatethetank’sPressure@Full,usethefollowingformula:
Pressure@Full=[Height@FullTank(feet)xSG]/2.31(feet/psi)
Pressure@Full=[Height@FullTank(meters)xSG]/0.704(m/psi)
Toselectthecorrectpressuretransmitter,followthestepsbelow:
1. MeasuretheHeight@FullTank(infeetormeters).
2. DeterminetheSGfortheliquid(ifthecustomerdoesnotknow,checktheMSDSsheet).
3. UsetheformulaabovetocalculatethePressure@Full.
a. Example:A16’tankwithaliquidmediaSGof0.9hasaPressure@Fullof6.23psi.
b. [(16’x0.9)/2.31’/psi]=6.23psi
4. SelectapressuretransmitterwithapressuregreaterthanorequaltothePressure@Full.
a. Intheexampleabovefora16’talltankwithaSG=0.9,youneedapressurerangegreaterthan
orequalto6.23psi.
b. Using a sensor with a pressure range of 15 psi provides a Maximum Liquid Height of 38.5’,
whichwillreadtheentirerangeofthe16’talltank.
c. Using a sensor with a pressure range of 5 psi provides a Maximum Liquid Height of 12.83’,
whichisshortby3.17’.
i. This means that the sensor will output 20 mA at 12.83’ of liquid and the top 3.17’ of
liquidwillnotbe
measured.
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