B - Temperatur-Shop

Thermal Detector
Detector in which the photons of incident radiation are converted to heat and then
into a signal from the detector. Thermal detectors include pyroelectric, bolometer, and
thermopile types.
Thermal Drift
See temperature coefficient.
Thermal Radiator
An object that emits electromagnetic energy due to its temperature.
Thermal Shock
An error due to a rapid change in the ambient temperature of an instrument. Expressed
as a maximum error and the time required for performance to return to prescribed
specifications.
Thermistor
A semiconductor material whose resistivity changes with temperature.
Thermocouple
A set of two junctions of two dissimilar metals used to measure temperature by means of
the Peltier effect, whereby heat is liberated or absorbed by the flow of electrical current
through a junction of two dissimilar metals such that an electrical potential develops
between two such junctions in proportion to the difference in temperature of the junctions.
A variety of types exist including:
J (Fe / constantan)
K (chromel / alumel)
T (Cu / constantan)
E (chromel / constantan)
R (Pt / Pt - 30 % Rh)
S (Pt / Pt -10 % Rh)
B (Pt - 6 % Rh / Pt - 30 % Rh)
G (W / W - 26 % Re)
C (W - 5 % Re / W - 26 % Re)
D (W - 3 % Re / W - 25 % Re)
Thermoelectric (TE) Cooling
Cooling based on the Peltier effect. An electrical current is sent through two junctions of
two dissimilar metals. One junction will grow hot while the other will grow cold. Heat from
the hot junction is dissipated to the environment, and the cold from the other junction is
used to cool.
Thermogram
A thermal photograph generated by scanning an object or scene.
Thermopile
A number of similar thermocouples connected in series, arranged so that alternate junctions
are at the reference temperature and at the measured temperature, to increase the
output for a given temperature difference between reference and measuring junctions.
Time Constant
The time it takes for a sensing element to respond to 63.2 % of a step change at the
target.
Transfer Standard
A precision radiometric measurement instrument with NIST traceable calibration in the
USA (with other recognized standards available for international customers), used to
calibrate radiation reference sources.
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Transmittance
The ratio of IR radiant energy incident on an object to that exiting the object.
Triple Point
The condition of temperature and pressure under which the gaseous, liquid, and solid
phases of a substance can exist in equilibrium. For water at atmospheric pressure, this
is typically referred to as its freezing point.
Two-Color Thermometry
A technique that measures the energy in two different wavelength bands (colors) in order
to determine temperature. The 2 color technique has been shown to be effective for correcting
errors due to partial blockage of the target caused by dust particles.
V
Valley Hold
Output of the minimum temperature measurement indicated by an instrument during the
time duration for which this display mode has been active.
Verification
Confirmation of a design with regard to performance within all prescribed specifications.
Vibration Test
A test where oscillatory or repetitive motion is induced in an object (as per MIL-STD-810
or IEC 68-2-6), which is specified as an acceleration in g?s and power spectral density
(PSD), after which the unit is tested for proper operation.
W
Warm-Up Time Absolute Zero
The temperature of -273.15 °C, -459.69 °F, or 0 K; thought to be the temperature at
which molecular motion vanishes and a body would have no heat energy.
Wet bulb temperature
The wet bulb temperature Tw, is the temperature of the moistenrd thermometer during
measurement of relative air humidity with the Aspirations-Psychrometer. A thermometer
covered with a moistened wool wick is exposed to a constant airflow. After some time,
temperature equilibrium is reached. Together with ambient temperature and total
pressure, the relative humidity can also be calculated from the wet bulb temperature