What is calibration?
Accuracy & precision
Inaccurate & unrepeatable
Precise but inaccurate
Accurate but imprecise
Accurate & precise
Accuracy & precision
Data distribution
2
4
3
1
Increasing error
True value
( 3 ) Accurate but imprecise
( 4 ) Accurate & precise
Increasing error
Inaccurate & imprecise ( 1 )
Repeatable but inaccurate ( 2 )
Sensitivity & resolution
1
2
3
4
5
CENTIMETRES
Resolution
Resolution is a measure of the smallest change of
indication possible (i.e. the discrimination that the
instrument can show).
Sensitivity
Sensitivity is the smallest change in stimulus (input)
that causes a change in output.
Traceability of measurement
What it isn’t
It is not an unsubstantiated claim of competence and traceability by an
agency saying “trust us we know what we’re doing”.
It is not an organisation that has not undergone any form of independent
external audit.
It is not achieved through a list of serial numbers claiming that instrument
#123 was calibrated against instrument #456 which was calibrated
against instrument #789. There is no assurance any instrument calibration
was performed in a competent manner.
It is not achieved by relying on a reference instrument that does not have
a current calibration.
It is not achieved by believing the unsubstantiated claims of accurate
traceable calibration made by instrument manufacturers and/or agents
who have no independent, external certification or accreditation.
Why use an accredited lab?
They have qualified, experienced staff
Properly calibrated testing equipment
An adequate quality assurance program
Suitable testing facilities
Traceability of measurements to national or
international standards
Unbiased results
Ramifications for uncalibrated
equipment
Measurement time can be wasted.
Results will not stand scrutiny in court.
Non compliance with ISO9000.
Equipment will lack preventative maintenance.
Current calibration sticker
Procedures
Sound Level Meters
Tested in accordance with IEC61672-3:2006 Sound level meters
Absolute calibration
Frequency and time weightings
Acoustical frequency weighting
Reference level linearity
Self generated noise
Tone-burst
Electrical noise
Peak C sound level
Electrical frequency weightings
Overload indicator
Additional tests performed following a method based on
DIN - Level frequency distribution.
Statistical levels
Procedures
Audiometers
Tested in accordance with the umbrella standard
IEC60645 - Audiometers
Audiometers are regularly calibrated to help maintain
optimal performance.