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PHYSICALMEASUREMENT
Tip1
Vibrations
Tip4
BodyHeat
Weighing isone step in thewholeprocessoranalysis chain, however, it can strongly influence thequalityof thefinalproduct.
Accurateweighing isessential toensurecontinuousadherence toprocess requirements. Inaddition toahigh-qualitybalance,
weighingaccuracy isalsodependenton the surroundingsand the interactionof theuser. The impactof these influences canbe
dramaticallydecreasedwithproperknowledge.METTLERTOLEDO, the industry leader inweighing, hasassembleda setof tips
and tricks tohelpyouminimize these influencesandachievebetterweighing results.
AvoidVibrationsandDrafts
Ideally, thebalance room shouldbe
situated in themost vibration-free
areaof thebuilding, andaccessed
througha slidingdoor. Locate the
balanceaway fromdoorsandareas
of high traffic toavoiddrafts.Donot
weighnearwindowsor near
radiators,which can cause strong
currentsof air thatmay interfere
with thebalance.Avoidplacing thebalance in theair flowof air conditioning
unitsor deviceswith fans, suchas computers.
TipsandTricks forWeighing
Tip2
ElectrostaticCharge
ElectrostaticCharge
from theWeighingVessel
Weighingvesselsand samplesmay
becomeelectrostatically charged,
particularly indryair.Metal is the
bestmaterial forweighingvessels,
andglass ispreferable toplasticas
it is less susceptible toelectrostatic
charge. Reduceweighingerrorsby
increasingatmosphericmoistureand
usingantistatickits.
ProtectBalance
fromBodyHeat
Heat radiating fromanoperator’s
bodymayhaveanadverseeffect on
weighingmeasurements.Where
possible, avoidusing thehands to
place theweighingvessel in the
weighing chamber, as this canalter
temperatureandatmospheric
humidity.Wear a lab coat to reduce
theeffect of thebody’s surface temperature.
Tip3
Light andHumidity
Influencesof Light,
TemperatureandHumidity
Weighing resultsare influencedby
temperature. Locate thebalanceona
window freewall, away fromdirect
sunlight (heat) and fromheat
radiating light fixtures, suchas light
bulbs. Keep the temperatureof the
roomas constant aspossible. The
relativehumidity (RH) shouldbe
between45and60%.Never operate thebalanceoutside the specified range
of 20 to80%RH. Temperaturegradientsbetween theweighing sampleand
the surroundingenvironment can lead toair currentsalong theweighing
vessel. Air flowingalong the sideof thevessel generatesanupwardor
downward force that affects theweighing result, impactingon reproducibility
andaccuracy. Alwaysacclimatize samples to the temperatureof the
laboratoryorweighing chamber.
Tip5
Leveling
LevelingyourBalance
Align thebalance: Todo this, check
that theairbubble is in the center
of the level indicator.Use the
leveling feet tomakeadjustments.
Youmust thenadjust the sensitivity
of thebalance. Theexact procedure
isdescribed in theoperating
instructions for thebalance.
TIP:
Toensureanddocument that
thebalance is correctly leveledevery time for example, to complywithGLP
andGMPwe recommend theExcellencePlus familyof balanceswith the
built-inautomaticwarning function “LevelControl”.
Tip6
Eccentricity
AvoidCorner LoadErrors
–Eccentricity
Alwaysplace theweighing sample
in themiddleof theweighingpan.
Thiswill prevent corner loaderrors.
Withmicroand semi-microbalances,
theweighingpan shouldfirst be
loadedoncebrieflyafter a relatively
longpause (>30min) todeactivate
the “initialweighingeffect”.
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