METREL MD 9880 Benutzerhandbuch Seite 15

METREL MD 9880
In the Thermal imaging mode the display crosshairs can be used to assist in
targeting, the highest temperature will be auto marked by a red cross, and the lowest
temperature will be auto marked by a blue cross. All markers can be turned ON or
OFF in the Settings. Multimeter continues to operate normally while the camera is on.
Press the HOLD button to freeze the thermal image frame.
Lens and camera field of view
This table lists the horizontal Filed of view (FOV), vertical FOV and IFOV for lens.
Focal Length
7.5mm
IFOV (Instantaneous Field of View) is the size of the object caught in the single pixel
on the detector. It is given as spatial angle with unit mrad. It depends on the lens and
detector size.
DTS is distance to spot. It is the distance at which the given size spot can be
theoretical
measured. At unity distance, the IFOV can be then directly translated to spot size.
For accurate temperature measurement, the spot has to be about three times the
size of DTS
theoretical
EXAMPLE:
The FOV of the camera is 21° x 21°, which is about 0.36x 0.36 rad. The detector
resolution is 80x80 pixel. Each pixel then covers about 4.53 mrad, which is IFOV.
This means that at 1m distance, each pixel is covering 4.53mm
Temperature can be accurately measured on about 13.6mm
turned the other way, DTS can be the calculated distance at which each pixel will
2
cover 1m space, which is about 220m. Thermal camera uses 7,5mm lens, so
knowing the IFOV gives the pixel size of the detector as 34um.
80m
Horizontal FOV
21°
.
�������� =
������
��ℎ������������������
������
����������������
80m
220m
Thermal camera and DMM operation
Vertical FOV
21°
���������� ��������
�������� ���������� ����������ℎ
1
=
��������
������
=
3
Spot size 1m x 1m
21°
15
IFOV
4.53mrad
2
actual space.
2
at 1m distance. If