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Optional a close-up lens is available for the pyrometer (only for optics 250). This optics is
screwed in front of the optics and provides a small spot size in the focus distance.
The following drawing and the table shows the size of the spots in mm in dependence of the
measuring distance. Values between the mentioned data can be calculated by interpolation. The
spot size for measuring distance 0 is the aperture diameter “D” of the optics.
Using the close-up lens slightly attenuates the measuring signal (due to the transmittance). To
get furthermore correct measuring results, the transmission of the close-up lens (90% for the
IGA 320/23) must be entered in the software InfraWin (see 4, Settings / parameter
descriptions). Alternatively the emissivity ε can be adapted: ε
Trans
= 0.90 x ε
Object
The spot sizes, mentioned in the table above, will be only achieved at the adjusted distance.
Decreasing or increasing the measuring distance enlarges the spot size. Spot sizes for
intermediate distances, which are not shown on the optical profiles, may be calculated using the
following formula:
Note: The InfraWin program includes a Spot Size Calculator that roughly
estimates the unknown values.