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Fixed Spot Thermometer
B
CAUTION
If the user calibration is adjusted away from its default value of 1000,
the factory calibration will be no longer valid. However, returning the
value to 1000 will restore the factory calibration.
What is it for?
IQ Series thermometers are factory calibrated against source temperatures that
are traceable to international standards. Therefore, the user calibration should
not normally need to be adjusted from its default setting of 1000.
However, some users may choose to use the user calibration facility – perhaps
to match the instrument to a locally maintained temperature standard, or to
compensate for energy loss through a viewing window.
What does it do?
Single wavelength thermometers detect incident radiation and convert this
detected radiation into a signal that is proportional to the incident power or
brightness. The user calibration is applied as a factor to this brightness signal.
The nominal setting of 1000 equates to a factor of 1 (the user setting is divided
by 1000) – giving no correction to the brightness.
_
Corrected
Brightness is non-linear with temperature, so to produce a final temperature a
linearization function must be applied.
_
Indicated
The linearization function f is complex but at any temperature is approximately
exponential – meaning that a fixed percentage change in brightness will
produce a linear change in temperature i.e. every 3% increase in brightness
might result in a 1 °C increase in indicated temperature. In this case changing
the user calibration setting from 1000 to 1030 (3%) would cause the indicated
temperature to rise by 1 °C.
How to use it?
Using %/C tables
User Guide
USER CALIBRATION
_
User
Calibratio
Brightness
=
1000
(
Temperatur
e
=
f
Corrected
n
∗
Brightness
_
)
Brightness
series
B - 1
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