Landcal Blackbody Source
Type R1500T
User Guide
Page 12
6 Using the Furnace
6.1 Introduction
The furnace has been designed to create a target of uniform temperature with a
high emissivity at short wavelengths for calibrating radiation thermometers. The
target is a conical cavity at one end of a hollow cylinder, and the thermometer
views the target along the axis of the cylinder.
The cone plays an important part in establishing uniformity of radiation emitted
by the target and when calibrating radiation thermometers the target size
requirements must be met by the cone. If the thermometer target size is so big
that the walls of the cylindrical block are viewed, a less accurate calibration will
result.
6.2 Measuring thermocouple/indicating controller
A thermocouple situated between the heating elements and the conical target is
used to measure and control the temperature. The controller's digital indicator
on the side of the furnace displays the temperature measured.
Agreement between the thermocouple measurement and a reference standard
radiation thermometer is better than ±20°C at 1500°C, ±10°C at 1000°C.
The errors are repeatable, and a correction curve can be obtained with a
Certicate of Calibration for the source. A UKAS (United Kingdom Accreditation
Service) Certicate of Calibration is available from LAND Instruments
International.
6.3 On-site use
The source is transportable, so it can be used either in the laboratory where the
radiation thermometers are brought to the source for checking or taken to site
where the source is used close to the thermometer installations.
Before taking to site it is recommended that the elements are removed from
the source and carried separately in the foam lined boxes provided. After
use it is recommended that if possible the source is left to cool to an internal
temperature of below 200°C and the elements again removed before shipment.
These precautions will extend the life of the heating elements.
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