RayTek 3i Operator's Manual page 78

Temperature Coefficient (or Ambient Derating)
An indication of the instruments ability to
maintain accuracy when the ambient condi-
tions are subject to a slow change or drift.
The temperature coefficient is usually
expressed as the percent change in accuracy
per degree change in ambient temperature.
For a rapid change in ambient conditions
refer to Thermal Shock.
Temperature Resolution
The minimum simulated or actual change in
target temperature that gives a usable
change in output and/or indication (per the
ASTM standard test method E 1256-88).
Thermal Shock
A short term error in accuracy caused by a
transient ambient temperature change. The
instrument recovers from its accuracy error
when it comes back into equilibrium with
the new ambient conditions.
Thermistor
A semiconductor material whose resistivity
changes with temperature.
Thermocouple
A junction, comprising two dissimilar met-
als, that develops a small voltage dependent
upon the temperature of the junction.
Typical thermocouples types include:
J iron/constantan
K chromel/alumel
T copper/constantan
E chromel/constantan
R platinum/platinum-30% rhodium
S platinum/platinum-10% rhodium
B platinum-6% rhodium/platinum-30%
rhodium
G tungsten/tungsten-26% rhenium
C tungsten-5% rhenium/tungsten-26%
rhenium
D tungsten-3% rhenium/tungsten-25%
rhenium
Thermopile
An arrangement of thermocouples in series
such that the alternate junctions are at the
measuring temperature and at the reference
temperature. This arrangement increases the
thermoelectric voltage.
Glossary-6
Time Constant
The time it takes for a sensing element to
respond to 63.2% of a step change at the tar-
get.
Transfer Standard
A precision radiometric measurement instru-
ment with NIST traceable calibration in the
USA (with other recognized standards avail-
able for international customers), used to cal-
ibrate radiation reference sources.
Transmittance
The ratio of IR radiant energy transmitted
through an object to the total IR energy
received by the object for any given spectral
range; the sum of emittance, reflectance, and
transmittance is unity.
Warm-Up Time
Time, after turn on, until the instrument will
function within specified repeatability (per
the ASTM standard test method E 1256-88).
Verification
Confirmation of accuracy.
Vibration Test
An oscillatory or repetitive motion test of the
instrument per MIL-STD-810D or IEC 68-2-6,
often specified as an acceleration in g's (1g =
9.81m/s 2 = 32.2 ft./s 2 ), over a frequency
range typically measured in Hertz (sec -1 ).
Raynger 3i Series Operator's Manual