1. INTERPRETATION OF CALIBRATION REPORTS

2. Selection of Calibration Agency Calibration Periodicity
What is Calibration ?
Why Calibrate ?
Selection of Calibration Agency
Calibration Periodicity
Review / Interpretation of a Calibration Report
Requirements of ISO for reporting results
Acceptance of Calibrations Reports
How we can get updated ?

3. What is Calibration ?
According to the International Organization for Standardization publication entitled International Vocabulary of Basic and General Terms in Metrology, Calibration is the set of operations that establish, under specified conditions, the relationship between values indicated by a measuring instrument, a measuring system or values represented by a material measure, and the corresponding known values of a reference equipment or material

4. Why Calibrate ?
Industries, Research Organizations and Factories worldwide spend millions of dollars annually to calibrate their instrumentation yet the tangible evidence of what has been obtained in return for this investment generally receives inadequate attention

5. Why Calibrate ?
Calibration is accepted as a performance comparison against a standard of known accuracy.
Calibration is done,
To ensure readings from an instrument are consistent with other measurements.
To determine the accuracy of the instrument readings.
To establish the reliability of the instrument i.e. that it can be trusted or traceable.

6. Types of Calibration
Accredited
Non Accredited
In house Calibration

7. Selection of Calibration Agencies

8. Calibration Agencies
In order to get valid calibration results with global metrology system and to provide globally accepted quality products / services, the selection of the calibration agency is crucial.

9. Selection of Calibration Agencies

10. Selection Criteria Calibration Range Sufficient Test Accuracy Ratio
Traceability
Better Calibration Measurement Capability
Availability of Services
Regulatory authority /Accreditation agency Requirements
Cost of calibration
Level /Position required in traceability chain

11. Calibration Range
When considering / selecting a lab for calibration service, it should be thoroughly verified that calibration points at which the UUC has to be calibrated are within the range of Calibrating lab’s scope of service.
Eg: For a calibrating a thermometer with a resolution of 1C at 100 C, we have to choose a Calibration Lab with a reference thermometer having a resolution of at least 0.1C and a range of more than C.

12. Test Accuracy Ratio
In a calibration procedure, the TAR is the ratio of the accuracy tolerance of the unit under calibration to the accuracy tolerance of the calibration standard used. [based on NCSL Glossary of Metrology-related Terms].

13. Traceability
Calibrating Laboratories should establish a chain of traceability through national / international standards.
Traceability is a property of the result of a measurement, providing the ability to relate the measurement result to stated references, through an unbroken chain of comparisons each having stated uncertainties.

14. Calibration Measurement Capability
Calibration & Measurement Capability (CMC) is the value of uncertainty assigned by any accreditation body for a calibration laboratory. It is the best uncertainty, that calibration laboratory can provide for any measurement with in the range of a specific parameter
Eg with a volume calibration

15. Calibration Measurement Capability
When a pipette has to be calibrated from a accredited calibration laboratory, scope of the lab should be verified whether it meets the requirements in terms of parameter, range and Calibration Measurement Capability (CMC).
Requirements :
Pipette is having a range of 10µl to 1000 µl with a resolution of 1 µl and an accuracy of ± 8 µl.

16. Lab 1
Lab 2

17. Calibration Agencies Comparison
Pipette is having a range of 10µl to 1000 µl with a resolution of 1 µl and an accuracy of ± 8 µl.
Lab 1
CMC  up to 1000 µl  ± 0.5 µl
Reference Mass  Class E2
Lab 2
CMC  up to 5000 µl  ± 8.0 µl
Reference Mass  Not mentioned
 Lab 1 can be chosen for the calibration for the above mentioned pipette

18. Availability of Service
Some of NABL accredited Calibration Providers
SlNo
Laboratory Name
District 1
Electronics Regional Test Laboratory South
Thiruvananthapuram 2
Meter Testing & Standards Laboratory 3
Alfatek Services 4
SCTIMST 5
Sophisticated Test and Instrumentation Centre
Kochi 6
Fluid Control Research Institute
Palakkad 7
Isotech Metrology Solutions

19. Regulatory Authority Requirements
To meet the accreditation requirements of foreign agencies like COFRAC, in house and traceable calibration may be sufficient.
NABL require accredited calibrations meeting it’s published specific criteria‘s. (e.g. Specific Criteria for Calibration Laboratories in Mechanical Discipline – NABL 122)
CE marking / GLP Studies may require accredited calibrations with approved work procedures, study protocols, traceability etc.

20. Cost of Calibration
Calibration cost can be optimized by choosing the right calibration agency having required scope and CMC.
Better scope means better quality, means more costly.

21. Position in Traceability Chain
Calibration of Mass Set in FCRI , NPL – Time constraint, Cost, Transportation etc

22. Selection Criteria in Nutshell
Factors to consider while choosing a calibrating agency
Check the accuracy required for unit under calibration (UUC) based on the tolerance desired.
Check the NABL scope of the calibrating laboratory whether it meets the requirement both for parameter, range and CMC.
The Error and uncertainty expressed should be in terms of % of reading in the calibration certificate and not in % of full scale (FSD).
Preference should be given to accredited calibration Laboratories since these labs fulfill the requirements of an international standard (ISO 17025) are considered to competent than other labs.

23. Calibration Periodicity

24. Calibration Periodicity
One of the most significant decision to be made regarding calibration is how often an instrument has to be calibrated.
Currently there is only some guidelines providing the necessary directions with respect to the calibration periodicity.

25. Calibration Periodicity
Some reference documents for fixing the calibration interval
ILAC G-24: Guidelines for the Determination of Calibration
NSCL RP1: Establishment and Adjustment of Calibration
NIST GMP-11 – Assignment & Adjustment of Calibration Intervals for Laboratory

26. Calibration Periodicity
Factors need to be taken into consideration while fixing calibration interval are
Type of Instrument
Frequency of Usage
Manufacturer’s recommendation
Maintenance and Service
Accuracy of measurement sought
Frequency of cross check
Penalty of incorrect measurement data getting accepts

27. Calibration Periodicity using penalty factor
New Calibration Interval = Current Interval * 50 / P
Where P is the penalty factor estimated for the instrument.
Reference :‘A practical approach for calibration interval’ (STQC)

28. Calibration Periodicity – Penalty Factors
Sl No
Factor
Penalty Factor
(Feature and Rating) 1
Accuracy
Very Fine 10
Coarse 2
Frequency of Usage
Very High
Very low 3
Construction / Type
Very delicate
Robust 4
Required Skill level in operation 5
Operating Environment
Shop Floor
Clean Area 6
Maintenance Requirement
Very frequent
Infrequent 7
Nature of measurement technique
New
Established 8
Age of the equipment
Very old
Relatively new 9
Stability of calibration
Very high
Cost of Calibration
Low
TOTAL
100 20

29. Estimating Calibration Periodicity
Sl No
Factor
Penalty Factor 1
Accuracy (± 1C) 2
Frequency of Usage (daily 2 times) 4 3
Construction / Type (Digital) 5
Required Skill level in operation (medium)
Operating Environment (Heated) 6
Maintenance Requirement (very low) 7
Nature of measurement technique (Established) 8
Age of the equipment (3 years) 9
Stability of calibration (Good) 10
Cost of Calibration (Rs.2500/cal)
TOTAL 40
For example, calibration periodicity of a digital thermometer can be estimated as, Calibration Interval, CI =( 1 * 50) / 40 = 1.25
 CI can fixed as 1 Year

30. When to recalibrate ?
In some cases equipments has to be recalibrated other than routine recalibration interval.
If the exact performance of the equipment is not known
If the equipment is under gone any repair.
If there is any doubt in the performance of the equipment.

31. Interpretation of Calibration Reports

32. Calibration Reports
Calibration Reports are the records that provides clients the results and outcomes of a calibration process.
Calibration reports / certificates are used for the following activities.
Applying correction to an instrument reading.
Characterizing the accuracy of an instrument.
Calculating the uncertainty in further measurement.

33. Applying correction
Thermometer calibration results
Corrected Temperature at 110 C is
= C
The spacing and number of points selected are sufficient to allow corrections for any reading to be deduced with sufficient accuracy by linear interpolation. As a general rule, extrapolation of corrections is not recommended.

34. Characterizing the accuracy
We can describe the variations in terms of the centre and the width of the distribution of readings.

35. Calculating the uncertainty
In estimating the uncertainty of a measurement, the equipment used as a reference has a role. In uncertainty calculation, the accuracy of the reference equipment and uncertainty of the reference equipment are major contributors of uncertainty.
The above mentioned uncertainty is available from the calibration certificate of reference equipment used.

36. Contents of Calibration Reports
When a Calibration Certificate for an equipment is received, it can be confusing to know what is important and how to interpret the information provided.
The report should contain,
The details about the UUC– Unit Under Calibration
The calibrating laboratory’s reference equipment details
The test method used
The results including the corrections
The uncertainty

37. Requirements of Calibration Reports
The ISO standard defines what are the things to be includes in a Calibration report, in it’s clause “5.10.2”.
The basic requirements are,
The Title: The calibration certificates establish what the document claims to be.
Name and address of calibration laboratory
The user and laboratory can trace all work relating to the calibration and the use of an instrument.
Each page should be numbered and the total number of pages given.
Unambiguous identification of the instrument, including make, model and serial number.

38. Requirements of Calibration Reports Contd.
Date of calibration
Identification of calibration method used or unambiguous description of any non-standard method used, and/or deviation from standard method
Conditions under which the calibration is carried out e.g.
Environment like ambient temperature, pressure, etc
Measurements and derived results
A statement of the estimated uncertainty of calibration results
A signature and title of person (s) accepting responsibility for the report contents
A statement that the certificate shall not be reproduced other than in full, except with the approval of Top Administrator of the Calibration Laboratory.

39. Sample Calibration Report
Details of Calibration Laboratory

40. Sample Calibration Report
Details of Accreditation of Calibration Laboratory

41. Sample Calibration Report
Unique Calibration Report ID

42. Sample Calibration Report
Details of Requesting Person / Organization

43. Sample Calibration Report
Details of Equipment Calibrated (Unit Under Calibrated)

44. Sample Calibration Report
Details of Authorized Personnel of Calibration Laboratory

45. Sample Calibration Report
Page number with number of pages in Calibration Report

46. Sample Calibration Report Contd…
Date of Calibration

47. Sample Calibration Report Contd…
Specification of Unit Under Calibration

48. Sample Calibration Report Contd…
Details of Environment during Calibration procedure

49. Sample Calibration Report Contd…
Details of Reference Equipments including calibration traceability

50. Sample Calibration Report Contd…
Details of CMC (Calibration & Measurement Capability) of Calibration Laboratory if it is accredited

51. Sample Calibration Report Contd…
Results of Calibration

52. Sample Calibration Report Contd…
Procedures & Standard documents adopted for calibration.

53. Sample Calibration Report Contd…
Details of Calibration Operators

54. Sample Calibration Report Contd…
End of Calibration Report

55. Acceptance of Calibration Reports
In order to receive “Technically valid Calibration / Test results competent to Global Metrology System, following actions can be taken.
Verify the accredited scope of the laboratory on Accreditation body’s web site whether it meets the requirement both for parameter, range and CMC.
Visit / enquire about the laboratory to verify its existence, available facilities, Competency and suitability to your requirement.
To protect the genuine accredited laboratories and to prevent the malpractices those are defaming the country, please do not encourage or do not collude in such activities like getting reports without performing actual calibration, Using of logo of accreditation bodies without proper information etc.
Providing review of report points

56. Updates

57. Updates
NABL India (
NPL India (
NPL UK (
Measurement Standards Laboratory, New zealand ; MSL (
National Association of Testing Authorities, Australia ; NATA (