Brookfield KU-2 - Interpretation of Calibration Check Results

Brookeld Engineering Labs., Inc. Page 12 Manual No. M04-242-E1213
 6) AfteryouhaverecordedresultsinKU,thenmovetheSelectorknobtothe"gm"positionand
recordyourreadingingrams.Ifyouareusingaprinter,threemeasurementswillbesenttothe
printerandwillprintoutassoonastheHoldDisplayswitchisswitchedbacktotheDOWN
position.
Interpretation of Calibration Check Results
When verifying the calibration of the KU-2, the instrument tolerance and viscosity standard uid
tolerancemustbecombinedtocalculatethetotalallowableerror.
TheKU-2isaccurateto±11grams,whichis1%ofthefullscalerangeingrams.TheBrookeld
ViscosityStandardisaccurateto±1%ofthestatedviscosityinKU.
ThetotalallowableerrorshouldbestatedinKU.Sincetheinstrumentaccuracyisstatedingrams,you
willhavetousethecomparisontable(TableA-2)andconvertfromgramstoKU.
Correctinterpretationofyourcalibrationresultsrequiresthatyoucompareyourreadingsingramsto
theequivalentinKU.Youmustthenbracketyourreadingwithupperandlowerlimitsbasedonthe
allowableerrorof±11.0grams.Convertthisacceptablerangeingrams(asdenedbytheupperand
lowerlimits)toKUunits.
Example: CalculatetheallowableerroroftheKU-2usinguidKU106;thestatedviscosity
oftheuidis104.8KU.Theviscometerindicatedameasuredviscosityof105KU
and410grams.
 1) Measuredresultsfromthecalibrationcheckingramswere410grams.Locate410gramson
theconversionchart(TableA-2).
 2) TheKU-2isaccurateto±11.0grams.Startingfrom410grams,count11placesaboveandbelow
the410grams.Thisiscalled"bracketing"theacceptablerange.Inthiscase,theacceptable
rangewillbefrom399gramsto421grams.
 3) Convert the acceptable rangein grams to KU. Locate the minimumand maximum grams
bracketed.LooktotherightofeachnumberfortheconversiontoKU.Inthiscase,itwillbe
103.9KUminimumand105.7KUmaximum.Thetotaldifferencebetween103.9and105.7
KUis1.8KU.Therefore,theaccuracyis±0.9KU.This is the accuracy for the Viscometer
in KU, ± 0.9 KU.
 4) Nowthatyouhavetheaccuracyfortheinstrument,youcanaddittotheaccuracyoftheuid.
Theuidisaccurateto±1%ofthestatedvalueinKU.Theviscositystandardiscalibratedat
104.8KU,±1%isequalto±1.0KU.
    0.9KU(instrumentaccuracy)
+1.0KU(uidaccuracy)
    1.9KU(totalallowableerror)
 5) Totalallowableerrorforthecalibrationcheckinthisexampleis104.8KU,±1.9KU(102.9KU
to106.7KU).Sincethemeasuredreadingof105KUfallswithinthisrange,theViscometer
isconsideredincalibration.