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Calibration of Thermometry Instruments

Calibration of Thermometry Instruments. Bangladesh BEST Programme. Nihal Gunasekara Sri Lanka. Essential Features of Calibration. Bangladesh BEST Programme. Fixed Point Calibration – Primary Level Primary Laboratories –NPL or NML

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Calibration of Thermometry Instruments

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  1. Calibration of Thermometry Instruments Bangladesh BEST Programme NihalGunasekara Sri Lanka

  2. Essential Features of Calibration Bangladesh BEST Programme • Fixed Point Calibration – Primary Level Primary Laboratories –NPL or NML • Comparison Calibration – Secondary Level Secondary Level Laboratories

  3. Fixed Point Calibration Bangladesh BEST Programme • Fixed Point Calibration – ITS-90 Fixed Points • Medium – Fixed Point Bath or Furnace • Advantage - Very Small Uncertainty

  4. Comparison Calibration Bangladesh BEST Programme • Comparison – Secondary Standard • Medium – Calibration Bath or Dry Well • Uncertainty – Larger than Fixed Point Calibration

  5. Bangladesh BEST Programme Calibration Hierarchy ITS 90 Fixed Points Black Body Radiation Source Optical Pyrometers upto 3500 °C Thermocouples Type R & S upto 1500 °C & Thermocouples Type B upto 1700 °C Standard Platinum Resistance Thermometers Upto 1000 °C Working Standard Platinum Resistance Thermometers upto 1000 °C Thermocouples upto 1700 °C Furnaces upto 3000 °C Platinum Resistance Thermometers Liquid in glass Thermometers Dial Thermometers Thermocouples Thermocouples upto 1000 °C Temperature Baths Ovens/Incubators Furnaces

  6. Calibration of Laboratory Equipment Bangladesh BEST Programme • Laboratory Ovens – Mainly used for sterilization of Glassware Normally upto 300 °C • Laboratory Incubators -  Mainly used forgrowing microbial cultures Normally upto 50 °C

  7. Performance Testing of Ovens/Incubators –Three Point Method Bangladesh BEST Programme Check the following before commence the test • Power supply and its socket • Temperature range/ indicator of the oven / incubator • Location of the built-in temperature sensor of the oven / incubator • Ventilation levels • Any other indicators, if available

  8. Selection of Test Temperatures Bangladesh BEST Programme • Select at least three test points which are approximately equally spaced covering the working range • If only one test point is requested select that test point • Oven with the range 50 °C to 250 °C select 50 °C, 100 °C, 150 °C, 200 °C and 250 °C • Select test point which are not within the ± 15 °C of the requested points by the customer • If the incubator is used for one/two test point/s select that/both test point/s

  9. Placement of Temperature Sensors Bangladesh BEST Programme • Place the temperature sensors in the “upper”, “middle”, “lower” and “near temperature sensor “ Near sensor Upper Middle Lower

  10. Steady-state Condition Bangladesh BEST Programme Stability “Obtain the readings after stabilized the temperature setting and ensure that the set temperature is stable before commence the record readings” .

  11. 150 100 80 Time (min.) t1 t2 Stability Conditions Bangladesh BEST Programme Temperature (° C ) t1 - t2 is the temperature stabilized period at 150 °C

  12. Data Recording Bangladesh BEST Programme • Record the maximum / minimum of the built in temperature indicator. • Record the temperature from all four test sites at 30 seconds time intervals during the “test interval” (i.e. one hour or three cycles of the controller, which ever is the longer), after stabilization. • Record ambient temperature and ambient relative humidity near the oven (i.e. about 1m away from the oven). • Repeat the above steps for each of the test temperature settings of the oven. • Record all data in a data recording sheet.

  13. Bangladesh BEST Programme Performance test results for an oven/incubator (three point)Specification:180 ±1oC

  14. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Enclosure temperature: mid-range value of the temperatures obtained from all relevant sites within the enclosure throughout the test interval. • Measured enclosure : enclosure temperature computed from the measured temperatures. It is equal to half the sum of the maximum and minimum indicated temperatures • Indicated enclosure temperature : enclosure temperature computed from indicated temperatures. It is equal to half the sum of the maximum and minimum indicated temperatures

  15. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Spatial variation: difference between the mid-range of all measured temperatures obtained at one site and that at another site for those sites which give the greatest difference. • Measured spatial variation: spatial variation computed from measured temperatures • Indicated spatial variation: spatial variation computed from indicated temperatures

  16. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Temporal variation: maximum value of the temperature range obtained for each standard site through out the test interval. • Measured temporal variation : temporal variation computed from measured temperatures • Indicated temporal variation : temporal variation computed from indicated temperatures

  17. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Maximum measured temperature : the highest measured temperature obtained during the test interval • Minimum measured temperature : lowest measured temperature obtained during the test interval • Overall variation:difference between the maximum and minimum measured temperatures.

  18. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Test site: location at which a test sensor is positioned for the purpose of temperature measurement during testing of the enclosure. • Mid-range value: half the sum of maximum and minimum values of a set of temperatures. • Temperature range: difference between the maximum and minimum values of a set of temperatures.

  19. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Definitions : • Test interval:interval of time to which the steady state characteristics. The test interval will commence after stability has been established and shall be of a sufficient period of time to characterize the temporal variation. • Apparatus required : A temperature data logger and a set of suitable thermocouples to cover the required temperature range of the incubator.

  20. Performance Testing of Ovens/Incubators – Multi- Point Method Bangladesh BEST Programme Inspection: • Power supply and its socket • Temperature range/ indicator of the oven or incubator • Location of the built-in temperature sensor of the oven or incubator • Ventilation levels • Any other indicators, if available

  21. Selection of Test temperatures - Oven Bangladesh BEST Programme • Select at least three test points which are approximately equally spaced covering the working range • If only one test point is requested select that test point • Oven with the range 50 °C to 250 °C select 50 °C, 100 °C, 150 °C, 200 °C and 250 °C • Select test point which are not within the ± 15 °C of the requested points by the customer • If the incubator is used for one/two test point/s select that/both test point/s

  22. Selection of Test temperatures- Incubator Bangladesh BEST Programme • Select the temperature settings designed for the incubator

  23. Bangladesh BEST Programme Performance test results for a laboratory oven/incubator (multi point) Temperature variation Temperature specification Grade of an oven/incubator Performance test results

  24. T1 T2 T3 T4 T5 T2 T7 T6 Bangladesh BEST Programme Temperature variation inside a chamber

  25. Bangladesh BEST Programme Temperature Specification T± ΔT oC Ex: 100 ±2.5oC

  26. Bangladesh BEST Programme Grade of an oven/incubator G = 8- 6.64log[100Rm/100+D] Where; G: Grade of the oven Rm: Maximum overall variation (Rm=2 ΔT) D : Difference between oven temperature and ambient temperature N = 3 + 3(G)0.6(V)0.2 Where; N: Number of standard test sites V: Volume of the oven

  27. Performance test results Bangladesh BEST Programme Test point:100 ± 2.5oC (temperature specification) Rm, Maximum overall variation=5oC D= 100-20oC G=5 N = 9

  28. Bangladesh BEST Programme Grade of an oven/incubator The above approximate values are provided as examples for guidance only

  29. Calculation and Derived Quantities Bangladesh BEST Programme The mid range temperature for the sensor = ½ ( t max + t min) Temperature range of the sensor = ( t max - t min ) Let for specific test temperature : T max is the largest t max value obtained from N test sites T min is the smallest t min value obtained from N test sites OVERALL VRIATION = T max – T min MEASURED ENCLOSURE TEMPERSTURE = ½ (Tmax + Tmin )

  30. Bangladesh BEST Programme Calibration Results

  31. Bangladesh BEST nProgramme ESTIMATION OF UNCERTAINTY Prepare the Uncertainty Budget as per Uncertainty of Measurement GUM JCGM 100 :2008 Calculate the CMC value for the scope of accreditation (not mote than 02 significant figures) Thereported uncertainty in your report should alwaysbegreater than CMC value

  32. Bangladesh BEST Programme Thank you

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