Presentations text content in 1 Calibration of Thermometry Instruments
Slide1
1
Calibration of Thermometry Instruments
Nihal GunasekaraSri Lanka
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Slide22
Essential Features of Calibration
Fixed Point Calibration – Primary Level Primary Laboratories –NPL or NML Comparison Calibration – Secondary Level Secondary Level Laboratories
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Slide33
Fixed Point Calibration
Fixed Point Calibration – ITS-90 Fixed PointsMedium – Fixed Point Bath or FurnaceAdvantage - Very Small Uncertainty
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Slide44
Comparison Calibration
Comparison – Secondary StandardMedium – Calibration Bath or Dry WellUncertainty – Larger than Fixed Point Calibration
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Slide5
Calibration Hierarchy
ITS 90 Fixed PointsStandard Platinum Resistance Thermometers Upto 1000 °C
Working Standard Platinum Resistance Thermometers
upto 1000 °C
Platinum Resistance Thermometers
Liquid in glass Thermometers
Dial Thermometers
Thermocouples
Thermocouples Type R & S
upto
1500 °C & Thermocouples Type B
upto
1700 °C
Thermocouples
upto
1700
°C
Thermocouples
upto
1000 °C Temperature Baths
Ovens/Incubators
Furnaces
Black Body Radiation Source
Optical Pyrometers
upto
3500 °C
Furnaces
upto
3000 °C
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Slide66
Calibration of Laboratory Equipment
Laboratory Ovens – Mainly used for sterilization of Glassware Normally upto 300 °CLaboratory Incubators - Mainly used for growing microbial cultures
Normally upto
50 °C
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Slide77
Performance Testing of Ovens/Incubators –Three Point Method
Check the following before commence the testPower supply and its socketTemperature range/ indicator of the oven / incubatorLocation of the built-in temperature sensor of the oven / incubatorVentilation levelsAny other indicators, if available
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Slide88
Selection of Test Temperatures
Select at least three test points which are approximately equally spaced covering the working rangeIf only one test point is requested select that test pointOven 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 customerIf the incubator is used for one/two test point/s select that/both test point/s
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Slide99
Placement of Temperature Sensors
Place the temperature sensors in the “upper”, “middle”, “lower” and “near temperature sensor “
Upper
Middle
Lower
Near sensor
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Slide10Steady-state Condition
Stability “Obtain the readings after stabilized the temperature setting and ensure that the set temperature is stable before commence the record readings” .
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Slide1111
Stability Conditions
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150
80
100
Time (min.)
t
1
t
2
Temperature
(° C )
t
1
- t
2
is the temperature stabilized period at 150 °C
Slide1212
Data Recording
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.
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Slide1313
Performance test results for an oven/incubator (three point)
Specification:180 ±1oCTemp. setting
(
o
C
)
Value of the indicator
(
o
C)
Measured mean value
(
o
C)
Exp.
Unce
.
(
o
C
)
k=2
Min
Max
Near the sensor
Upper
area
Middle
area
Lower
area
180.0
180.0
179.9
180.1
180.5
180.3
181.1
±0.3
Uncertainty component=
Exp.Unc
/2
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Slide1414
Performance Testing of Ovens/Incubators – Multi- Point Method
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 temperaturesIndicated enclosure temperature : enclosure temperature computed from indicated temperatures. It is equal to half the sum of the maximum and minimum indicated temperatures
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Slide1515
Performance Testing of Ovens/Incubators – Multi- Point Method
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
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Slide1616
Performance Testing of Ovens/Incubators – Multi- Point Method
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 temperaturesIndicated temporal variation : temporal variation computed from indicated temperatures
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Slide1717
Performance Testing of Ovens/Incubators – Multi- Point Method
Definitions :Maximum measured temperature : the highest measured temperature obtained during the test interval Minimum measured temperature : lowest measured temperature obtained during the test intervalOverall variation: difference between the maximum and minimum measured temperatures.
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Slide1818
Performance Testing of Ovens/Incubators – Multi- Point Method
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.
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Slide1919
Performance Testing of Ovens/Incubators – Multi- Point Method
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.
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Slide2020
Performance Testing of Ovens/Incubators – Multi- Point Method
Inspection:Power supply and its socketTemperature range/ indicator of the oven or incubatorLocation of the built-in temperature sensor of the oven or incubator Ventilation levelsAny other indicators, if available
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Slide2121
Selection of Test temperatures - Oven
Select at least three test points which are approximately equally spaced covering the working rangeIf only one test point is requested select that test pointOven 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
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Slide2222
Selection of Test temperatures- Incubator
Select the temperature settings designed for the incubator
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Slide23
Performance test results for a laboratory oven/incubator (multi point)
Temperature variation
Temperature specificationGrade of an oven/incubatorPerformance test results
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Slide24Temperature variation inside a chamber
T1
T2
T3
T2
T4
T5
T6
T7
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Slide25Temperature Specification
T± ΔT
oC Ex: 100 ±2.5 oC
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Slide26Grade of an oven/incubator
G = 8- 6.64log[100R
m/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
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Slide2727
Performance test results
Test point:100 ± 2.5oC (temperature specification)Rm, Maximum overall variation=5oCD= 100-20oC
G=5 N = 9
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Slide28Grade of an oven/incubator
Grade (G)
Max. permissible overall variation (Rm ) °C
D = 30
D = 100
4
5.2
8.0
6
2.6
4.0
8
1.3
2.0
9
0.92
1.4
12
0.33
0.5
14
0.16
0.25
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The above approximate values are provided as examples for guidance only
Slide2929
Calculation and Derived Quantities
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 (
T
max
+
T
min )
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Slide30
30
T/C Position
Maximum
(
o
C
)
Minimum
(
o
C
)
Difference
(
o
C
)
Mid range
(
o
C)
Exp.Unc
(
o
C), k=2
1
100.9
100.8
0.1
100.8
±0.3
2
100.5
100.3
0.2
100.4
3
99.9
99.8
0.1
99.8
4
99.0
98.8
0.2
98.9
5
100.2
100.0
0.2
100.1
6
100.5
100.2
0.3
100.4
7
100.2
100.0
0.2
100.1
8
97.9
97.4
0.5
97.6
9
100.8
100.7
0.1
100.6
Indicator value
100.6
100.5
0.1
100.6
Indicated Enclosure temperature = 100.6
o
C
Measured enclosure temperature = 99.2
o
C
Spatial variation = 3.2
o
C
Temporal variation = 0.5
o
C
Overall variation=3.5
o
C Grade = 6
Calibration Results
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Slide31ESTIMATION
OF UNCERTAINTY
Prepare the Uncertainty Budget as per Uncertainty of Measurement GUM JCGM 100 :2008Calculate the CMC value for the scope of accreditation (
not mote than 02 significant figures)
The
reported uncertainty
in your report should
always
be
greater than CMC value
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Slide32Bangladesh BEST
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Thank you
1 Calibration of Thermometry Instruments
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