Fluke Ti20 - Manual (Page 54)

Ti20
Users Manual
A-4
Level
Level is the median point of a given temperature scale. For example, if the unit is
currently in Automatic mode, and there is a given thermal scene with MIN and MAX
temperature limits, the moment you switch the unit to Manual mode, the Level value is
set by the unit according to the following formula:
2
Max Span
Level =
+ Min Span
dag129f.eps
Micron (or µm)
10
-6 meters (m), or 0.000001 m.
Minimum spot size
The smallest spot an instrument can accurately measure.
NETD
Noise Equivalent Temperature Difference. Peak to peak system electrical noise normally
measured at the output (display or analog) expressed in °F or °C.
NIST Traceability
Calibration in accordance with and against standards traceable to NIST (National
Institute of Standards and Technology, USA). Traceability to NIST is a means of
ensuring that reference standards remain valid and their calibration remains current.
Non-Gray Body
A radiating object that is partly transparent to infrared (transmits infrared energy at
certain wavelengths); also called Colored Bodies. Glass and plastic films are examples of
non-gray bodies.
Optical Pyrometer
A system that, by comparing a source whose temperature is to be measured to a
standardized source of illumination (usually com-pared to the human eye), determines the
temperature of the former source.
Optical Resolution
The distance to size ratio (D:S) of the IR measurement spot, where the distance is usually
defined at the focus distance, and the size is defined by the diameter of the IR energy spot
at the focus (typically at the 90% IR energy spot diameter). Optical resolution may also
be specified for the far field by using values of far field distance and spot size.
Pyroelectric Detector
Infrared detector that behaves as a current source with an output proportional to the rate
of change of the incident IR energy.
Radiation Thermometer
A device that calculates an object’s temperature (given a known emissivity) from
measurement of either visible or infrared radiation from that object.
Reflectance
The ratio of the radiant energy reflected off a surface to that incident on the surface; for a
gray body this is equal to unity minus emittance; for a perfect mirror this approaches
unity; and for a blackbody the reflectance is zero.