GHM Delta OHM LPPIRG01, Operating Manual, Page: 5 / 26

LPPIRG01
- 5 -
V2.1
E
FIR
↓
= E
term
+
σ
T
B4
(1)
Where:
E
term
= net radiation (positive or negative) measured by the thermopile (W m
-2
);
σ = Stefan-Boltzmann constant (5.6704 x 10 -8 W m -2 K -4 );
T
B
= pyrgeometer temperature (K), obtained by the reading of the NTC resistance (see
table 5.1).
E
term
is calculated from the sensitivity of the instrument C [
µ
V/(W m
-2
)] and from the
output signal U
emf
according to formula 2:
E
term
= U
emf
/ C
(2)
The first term of formula 1 represents the net radiation, that is to say the difference
between ground infrared radiation and the pyrgeometer emission, while the second term
is the radiation emitted by an object (assuming emissivity
ε
=1) at temperature T
B
.
Fig. 2.2: scheme of principle LPPIRG01 (version with mV output)
To prevent internal condensation forming on the internal side of the window under cer-
tain climatic conditions, silica gel tablets are inserted inside the pyrgeometer to absorb
humidity.
Thermopile
Surge
Protector
Connector pins
Housing
Cable
shield
NTC