Page 9
User Guide
Landcal P80P
Calibration Source
Values of between ±0.01K (±0.02°F) and ±0.1K (±0.2°F) are typical for
the uncertainty. A value of ±0.05K (±0.1°F )and ±0.2K (±0.4°F) should be
specified for the resolution depending on the type of measuring equipment
used.
As the emissivity of the source is less than 1.00, the radiance temperature
will be dependent on the wavelength of the thermometer under test. For
example a source operating at a temperature of 50°C (122°F) with emissivity
of 1.00 will show a temperature of 50°C (122°F) for a thermometer having a
pyroelectric (wavelength = 8 to 14µm) detector. However, a source operating
with emissivity of 0.995 at 50°C (122°F) for the same thermometer, will show
a radiance temperature of 49.6°C (121.3°F) for the same thermometer.
Most hand held thermometers and fixed installation thermometers used
in conjunction with an indicator have a resolution of ±1K (±2°F). Fixed
installation thermometers, whose output is measured on a digital voltmeter,
will have a resolution of between ±0.1K (±0.2°F) and ±0.5K (±1.0°F).
Any temperature gradients within the source will cause a difference between
the temperature as measured by the resistance thermometer and the true
radiance temperature of the source. A value of ±0.3K (±0.6°F) is typical.
To determine the best measurement capability, the uncertainty of each
individual measurement component should be added together. Typical values
would be between ±0.5K (±1°F) and ±3K (±6°F).
7.4 Calibration procedures
When calibrating radiation thermometers, it is important to follow
documented step by step procedures to ensure that specified calibration
conditions, such as calibration distance, furnace temperature and aperture
size are always met.
If difficulty is experienced in writing procedures, LAND would be pleased to
offer guidance as to what calibration conditions should be adopted for LAND
products.