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Page 8
Landcal P80P
Calibration Source
User Guide
7 Calibration of Radiation Thermometers
7.1 Preparation
The control setting will usually be the normal working temperature of the
thermometer to be tested.
For calibration checks that are traceable to National Standards the
target temperature is that indicated by the standard platinum resistance
thermometer. If traceability is not required the source can be used without
the resistance thermometer. From previous work the temperature as
shown on the control indication has been found to agree with the radiance
temperature to within ±2K.
To make the lining up of LAND fixed installation radiation thermometers
simpler an optical bench assembly is offered as an optional extra. When the
source is stood on the optional transportation case, the bench to mid target
dimension equals that of the optical bench assembly. Portable radiation
thermometers are usually hand held.
Position the holder on the optical bench to obtain the desired distance
between target and thermometer. By adjusting the vertical and transverse
vernier screws confirm that the holder is sighted correctly.
7.2 Thermometer calibration
When soaked conditions have been obtained, place the thermometer in the
holder and measure the thermometer output on the measuring apparatus.
Immediately after measure the output from the standard platinum resistance
thermometer.
Convert both outputs into temperature by reference to the relevant calibration
tables and compare.
7.3 Accuracy of calibration
The source has been designed for the accurate calibration of LAND radiation
thermometers. The accuracy that can be achieved by using the source is
dependent upon:
1) The uncertainty of calibration and resolution of the measuring resistance
thermometer.
2) The emissivity of the source.
3) The resolution of the radiation thermometer under test.
4) The temperature gradients present in the source.
The uncertainty of the resistance thermometer, specified on the calibration
certificate issued by the calibration laboratory, will be a function of:-
1) The calibration laboratories capabilities.
2) The type of resistance thermometer under test.
3) The temperature range covered.