DeltaOHM HD2402, Руководство по эксплуатации

Страница: 25 / 58

HD2402
- 25 -
V1.4
6.4.1 Geometrical parameters
The instrument measures irradiance, while radiance value must be known for calculat-
ing some exposure limit values (ELV). If geometric parameters are known, both quan-
tities can be calculated (the solid angle subtended from source to sensor must be
known) through calculation of the geometric parameter F.
The expected geometries are 5:
o
Geometric data not available : the event is contemplated, where no indication
can be provided on the source geometry. In this case, data supplied by the
software will be less complete, details are specified in the following paragraphs
illustrating ELV calculation.
o
Alpha [deg] : the user supplies the source angular dimension in degrees.
o
Omega Solid Angle [sr] : the user supplies the solid angle under which the
source is seen by the measurement device (the measurement unit is the stera-
dian).
o
Side d1 [m] - Side d2 [m] – Distance R [m] : assuming that the source has a
rectangular shape whose side lengths are d1 and d2 at R distance from the
measuring device (where the three quantities are expressed in meters), the
software provides for the calculation of the angle (alpha) and of the solid angle
(omega) subtended from the source to the measuring device. Calculation can
be correctly performed by selecting the
Alpha Omega rigorous calculation box
or in an approximate way. In this mode, the angles subtended by the two sides
of the rectangle are calculated with the formula:
] [ 1
1
rad
R
d
=
α
] [ 2
2
rad
R
d
=
α
o
Diameter d [m] – Distance R [m] : assuming that the source has a circular
shape with diameter d and is at R distance from the measuring device (both
measurements are expressed in meters) the software provides for the calcula-
tion of the angle (alpha) and of the solid angle (omega) subtended from the
source to the measuring device. Calculation can be correctly performed by se-
lecting the Alpha Omega rigorous calculation calculated with the formula or in
an approximate way. In this mode, the angle subtended from the source with
respect to the measuring device is calculated with the formula:
] [ rad
R
d
=
α
Once the solid angle is known, the radiance L
i
[W/(m
2
sr)] is given by the formula:
F
E
L
i
i
=
Where:
E
i
is the irradiance measured in W/m
2
;
F is the geometric parameter in steradians, as described at paragraph 2.2 at page 9.
If the
non rigorous calculation option (suitable for small angles) was selected, F= Ω in
all the mentioned cases.