weigh balance

8/7/2019 Weigh Balance

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Care and Maintenance

of the Weigh Balance


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Ohaus Voyager SeriesOhaus Voyager Series

Weigh BalanceWeigh Balance


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Importance of CalibratingImportance of CalibratingWeigh BalanceWeigh Balance

To ensure that the instrumentTo ensure that the instrumentaccurately weighs substances foraccurately weighs substances forreagent preparationreagent preparation


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Weigh Balance LocationWeigh Balance Location

Best environment for aBest environment for aweigh balance:weigh balance:

Free of vibrationFree of vibration

No large temperatureNo large temperature

fluctuationsfluctuations

No direct sunlight andNo direct sunlight and

No draftsNo drafts


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Weigh Balance CalibrationWeigh Balance Calibration

Calibration is important toCalibration is important toensure that the instrumentensure that the instrumentaccurately weighsaccurately weighssubstances for reagentsubstances for reagentpreparationpreparation

Test results may beTest results may be

incorrect due to instrumentincorrect due to instrumentmalfunctionmalfunction


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Use NIST Class S weights forUse NIST Class S weights forcalibrationcalibration

Verify that class S weights and balanceVerify that class S weights and balancepan are free from dust and fingerprintspan are free from dust and fingerprints

Only UserOnly User calibration will becalibration will be

discussed herediscussed here Note:Note:NEVERNEVERtouch the weights or thetouch the weights or the

balance pan with bare hands!balance pan with bare hands!

Weigh Balance CalibrationWeigh Balance Calibration(continued)(continued)


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The User method is used to calibrateThe User method is used to calibratethe balance using a mass of knownthe balance using a mass of knownvaluevalue

Three readings should be taken for theThree readings should be taken for thesix specified weights: 50, 100, 200,six specified weights: 50, 100, 200,500, 2000 and 4000500, 2000 and 4000

Record value in gramsRecord value in grams

User Calibration MethodUser Calibration Method


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Place selected mass value onPlace selected mass value on

balance panbalance pan

Record reading of weight of theRecord reading of weight of thecalibration masses. Removingcalibration masses. Removing

masses from pan returns balance tomasses from pan returns balance toweighing mode.weighing mode.

User Calibration MethodUser Calibration Method(continued)(continued)


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Balance Calibration WorksheetBalance Calibration Worksheet

Document eachDocument eachtime the balance istime the balance iscalibratedcalibrated

How often?How often?

Log should containLog should containat least theat least thefollowingfollowinginformation:information:

Balance Calibration Worksheet

Laboratory: ___________________

Balance: ______________________

alibration

heckDate: __________

Technician: ____________________

Precision/Repro

cibility: 0.1 mg

1 mg 10 mg 50 mg1. ______ 1. ______ 1. ______

2. ______ 2. ______ 2. ______

3. ______ 3. ______ 3. ______ Avg. ____ Avg. ____ Avg. ____

1 g 100 g1. ______ 1. ______ 2. ______ 2. ______

3. ______ 3. ______

Avg. ____ Avg. ____

ensitivity

erification:

Date Tech 10 mg 10 mg + 1 mg 50 mg 50 mg + 1 mg 100 g 100 g + 1 g

eviewed by: ____________________ Date: _____________


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Verify Sensitivity of the BalanceVerify Sensitivity of the Balance

To check sensitivity of the balance, keepTo check sensitivity of the balance, keepweighing paper on balance panweighing paper on balance pan

Make sure the balance reads zeroMake sure the balance reads zero Using tweezers, gently place the 10 mgUsing tweezers, gently place the 10 mg

weight on the balance weighing panweight on the balance weighing pan

fter the balance stops fluctuating, readfter the balance stops fluctuating, readthe weighing and record on the alancethe weighing and record on the alanceCalibration WorksheetCalibration Worksheet


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Verify Sensitivity of the BalanceVerify Sensitivity of the Balance

(continued)(continued)

While the 10 mg weight remains on theWhile the 10 mg weight remains on thebalance pan, using the tweezers, gentlybalance pan, using the tweezers, gently

add the 1 mg weightadd the 1 mg weight fter the balance stops fluctuating, recordfter the balance stops fluctuating, record

the reading in the alance Calibrationthe reading in the alance CalibrationWorksheetWorksheet

Repeat the above steps for each weighingRepeat the above steps for each weighingto complete the Sensitivity Verificationto complete the Sensitivity Verificationsection on the alance Calibrationsection on the alance Calibration

WorksheetWorksheet


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Maintenance and Care of BalanceMaintenance and Care of Balance

Keep balance cleanKeep balance clean -- daily, wipedaily, wipebalance with a damp clothbalance with a damp cloth

mild detergent may be usedmild detergent may be used

Never weigh materials directly onNever weigh materials directly onweigh panweigh pan

Keep calibration masses in a safe, dryKeep calibration masses in a safe, dry

placeplace Never touch the masses with bareNever touch the masses with bare

handshands

Cover balance when not in useCover balance when not in use

weigh balance

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