June 2004 slide 1

Calibration basics

Kjell BerghNemko

June 2004 slide 2

What is calibration

Relate measurement to SI unitsTraceabilityProof of functionality

Known uncertaintyUncertainty of calibration processAccepted deviation of instrument to ”true” value, Tolerance level

StandardsWhat is a standard?

June 2004 slide 3

Traceability

StandardsStandard vs. standard ! (Physical object vs. document)

SI-unitsInternational standardsNational standardsSub-standardsTertial standardsLower-level standards

June 2004 slide 4

SI units

Basic unitsMass (Kilogramme = kg)Length (Meter = m)Time (Second = s)Electric current (Ampere = A)Temperature (Kelvin = K)Luminance (Candela = cd)Molecular mass (mol)

Derived unitsFrequency (Hertz = Hz = s-1)Force (Newton = N = m*kg/s2)Pressure (Pascal = pa = N/m2)Energy (Joule = J = N*m)Power (Watt = W = J/s)Electric charge (Coulomb = C = A*s)

Derived unitsElectric potential (Volt = V = W/A)Capasitance (Farad = F = A*s/V)Inductance (Henry = H = V*s/A)Resistance (Ohm = Ω = V/A)Conductance (Siemens = S = A/V)Magnetic flux (Weber = Wb = V*s)Magnetic induction (Tesla = T = Wb/m2)Light flux (Lumen = lm = cd*sr)Light intensity (Lux = lx = lm/m2)

June 2004 slide 5

Accreditation

Calibration labISO 17025

QA-system of organizationPersonell ProceduresInternal surveillanceScope of accreditation

June 2004 slide 6

QA-system

Certified to ISO standard 17025Management, command structurePurchase handlingAssignment handling, billingObject reception and deliveryObject handling during calibrationPersonnel training and competenceProcedure maintenance, update

June 2004 slide 7

Personnel

QA-systemEducational standardCompetence maintenance, trainingIntegrity, independence of economic factors

PersonnelResponsibilityProcedure loyality

June 2004 slide 8

Procedures

Step-by-step for measurement set-upEnvironmental conditions (temp, ventilation,vibration, etc.)Acclimatization of calibration objectCalibration status of control instruments/standardsStep-by-step performance of measurementCompetence of personnel

June 2004 slide 9

Internal surveillance

QA-systemInternal proceduresPreventive actionsRegularity

June 2004 slide 10

Scope

Basic unitsList all units with accredited certificate

Derived unitsDocument how these may be derived from basic unitsHow this is related to accreditation

Objects for calibrationAre the important parameters covered by accreditation?How much can one rely on the basic accreditation?Let Cal.lab. document how non-accredited parameters can be covered by the general accreditation.

June 2004 slide 11

UncertaintyCal. object

May show small/acceptable deviation from ”true” valueStabilityParameter dynamic rangeSystem noise influenceImpedance mismatch

Cal. lab.Uncertainty of used sub-standardsUncertainty of cal. procedure

Influence of environmentInfluence of operatorInfluence of method

June 2004 slide 12

External vs. in-housecalibration

Specialized calibration labAccreditation costCompetenceEquipmentTraceabilityEfficiency

In-houseLess transportation costLess time delayExpenses to maintain