meterology the science of measurement

www.alliancecalibration.com

Metrology:The Science of Measurement


A Bit About Me

Kevin Radzik with Alliance Calibration

ASQ CCT since 2009

Technical Manager P&T(Process & Test)

10+ Years in the Pharmaceutical Industry• Working “in-house” to manage calibration

programs

• Contractor providing calibration & control services to the pharmaceutical industry


Metrology vs. Calibration

Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement.

“Metrologia” in ancient Greek meant the “Theory of Ratios”

Calibration is the comparison of a “standard” of known accuracy to an artifact of unknown accuracy.


Calibration where you didn't know it existed...

Items like deli scales and fuel pumps are calibrated and certified by local government agencies to protect customers.

With gas at $4/gallon they make sure you are getting what you pay for!


Calibration where you didn't know it existed...

Restaurant chains develop recipes in laboratories and refine them to be used in their restaurants in the simplest method possible. For example deep fry for 3:00 minutes.

If the laboratory didn't calibrate their instruments they could end up producing overcooked or worse, undercooked food

And serving raw chicken would

be very bad for business!!


How Calibration Works

Direct Comparison

2-Devices are simultaneously measuring the same quantity under the same conditions



Transfer

The use of a known artifact (i.e. gage block or mass) to test a measuring device.



Intrinsic

Standards that posses a measurable quantity by their nature

Triple-Point of Water cell is 0.01°C with an error as low as 5 mK


Traceability

Traceability is established by an unbroken chain of comparisons to a NSI (National Standards Institute)

Each level of comparison will add to the error of the measurement performed


ISO 17025 Accreditation

ISO 17025 was developed to standardize the way in which laboratories perform and report calibration and testing data.

ISO 17025 accreditation bodies such as LAB, A2LA, NAVLAP, A-CLASS, ANAB and others ensure compliance to the standard. Accreditation bodies recognized by ILAC are all considered equivalent.

Accreditation is good assurance that a lab has the proper tools & practices in place to perform calibrations with confidence.


“Hands-On” Demonstration

How long is a piece of string

On each table there is a calibrated ruler and several pieces of string. Please take a moment and work together to attempt the most accurate measurement of a “piece of string” possible


Problems?

Straightness Frayed Edges

Pulling Force Resolution of the ruler

Lighting Conditions Eyesight

Temperature HumidityEvery measurement apparatus has limitations. These limits impose a degree of error in every measurement made.

With more specialized equipment we can make better and better measurements, but there will always be an element of error based on various conditions.

Measurement uncertainty is used as a method to quantify the error present in any measurement.


Measurement Uncertainty

All sources of error in a given measurement must be quantified, and accounted for.

The number sources of error can be as few as: accuracy of the standard, uncertainty of the standard, resolution and repeatability.

However other items can also influence the measurement, such as: temperature, temperature Δ, barometric pressure, altitude, humidity, and the uncertainty of whatever instruments are used to measure these.



The ISO document “Guide to the expression of Uncertainty in Measurement” (the GUM) defines the way in which measurement uncertainty is calculated.

Contributing factors are quantified and corrected to represent 1σ using divisors based on the type of contribution the error provides.



The normalized contributors are then combined using the “Root of the Sum of Squares” and multiplied by a confidence factor.

The confidence factor of k=2 is most commonly used, and provides an approximately 95% assurance that the true value of the measurement is reported within the limits of the measurement uncertainty.

Measurement uncertainty defines the “gray area” inside of which the true value of a measurement lies.


Calibration Tracking

In the short term calibration provides a reasonable assurance that an instrument is fit to be used for the task for which it was designed.

However, long term evaluation of calibration data can provide increased confidence or even predict when a device is likely to “drift” out of specification under normal use.



At Alliance Calibration we provide our customers free access to our eTracking system as an easy way to keep all your calibration data in one easy to use web site.



There are several additional products available to track calibration data, the important thing is to use the tool that works for you.

In many industries calibration cycles are mandated by standards, but in industries where they are not long term trending of calibration data can be valuable in determining calibration cycles to be the most cost effective.


Long Term TrendingPlotting data over time and noting when adjustments or repairs were required is an excellent method to visually represent an instrument's history.

As more history is recorded it becomes easy to predict when future failures are likely.

And when anomalies occur along the trend they become noticeable and point to possible problems elsewhere in the quality system.


Questions & Comments

Thank you!!

meterology the science of measurement

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