Download - Metrology - Los Angeles Mission College
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What is Metrology?
▪ Metrology is the science of measurement.
▪ Most common types of measurements:
–weight, distance, volume, temperature, pH
▪ Scientific system of measurement:
Metric System
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Importance of Accuracy
▪ Accuracy in measurement is key to the generation of a
consistent product.
–accuracy depends on a regular process of testing and
calibrating (adjusting) instruments to be within an established
margin of error
• Random Error – fluctuations from measurement to measurement
• Systematic Error – consistent errors due to state of instrument
***Testing and Calibration typically involves following an SOP***
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Margin of Error Example (Micropipets)
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Equipment for Measuring Weight
▪ Triple beam balance
Photo courtesy of Ohaus Corporation
▪ Electronic balance
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Equipment for Measuring Weight
▪ Analytical balance
–Most accurate, measures to the
most significant figures (to the 10th
of a milligram or 0.0001)
–Contains an enclosure to eliminate
air currents
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▪ Substances are never weighed directly onto the scale
but into:
–weigh boats
–weigh papers
–other vessels such as a beaker
–scale must be zeroed or tared with the empty
paper/boat/vessel first
Equipment for Measuring Weight
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Equipment for Measuring Volume
▪ Graduated cylinders
–generally range in capacity from
10 ml to 1 liter or more
–best choice for larger volumes
–measured by the bottom of the
meniscus
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The Meniscus of a Measured Liquid
measure
bottom of
meniscus
A meniscus is the curved upper surface
of a liquid due to surface tension with
regard to the container (usu. glass).
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▪ Serological pipets
– require motorized or manual pipet
pumps or bulbs
–generally range in capacity from
1 ml to 25 ml
Equipment for Measuring Volume
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▪ Transfer pipets
–used for convenience, not
accuracy
–generally range from 1 to
3 ml in capacity
–may or may not be
graduated
Equipment for Measuring Volume
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▪ Adjustable-volume micropipets
–most accurate way to measure
volumes from less than 1 ml to
1000 ml
– require disposable pipet tips
Equipment for Measuring Volume
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▪ Erlenmeyer flasks, beakers
–generally used for mixing and short term
storage of solutions
–not very accurate for measuring
Equipment for Measuring Volume
beakers
Erlenmeyer flask
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▪ Reagent bottles
–used exclusively for long term
storage, not good for measuring
–requires proper labeling• name of solution
• concentration
• date made
• initials of person who made it
• potential hazards if necessary
Equipment for Storing Liquids