User Guide
Landcal Blackbody Source
Type P1600B2
Page 19
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 furnace operating at 1000°C / 1832°F with emissivity of 1.00 will
show a temperature of 1000°C / 1832°F for a thermometer having a silicon
cell (wavelength = 1µm) detector, and a temperature of 1000°C / 1832°F for a
thermometer having a pyroelectric (wavelength = 8 to 14µm) detector.
However, a furnace operating with emissivity of 0.998 at 1000°C / 1832°F
will show a temperature of 999.8°C / 1831.6°F for a thermometer having a
silicon cell detector, and a radiance temperature of 998.5°C / 1829.3°F for a
thermometer having a pyroelectric detector.
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 and ±0.5K / ±0.2°F and ±1.0°F.
To determine the best measurement capability, the uncertainty of each
individual measurement component must be added together. Typical values at
1000°C are between ±3K and ±5K / ±6°F and ±10°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 you experience any difficulty in writing your own procedures, LAND
Instruments International are pleased to offer guidance as to which calibration
conditions should be adopted for LAND products.
