Gossen Mavomonitor - Manual (Page 6)

6 GOSSEN Foto- und Lichtmeßtechnik
4 Functioning and Circuitry
The instrument essentially comprises the sensor
containing the silicon photocell and the correction
filters and the instrument itself. In an integrated
(IC) operational amplifier the short-circuit current
of the photocell, which is located directly at the
input to the op amp, is measured. This kind of
short-circuit current measurement has the advan-
tage of low dependency on temperature and pro-
ducing a linear result. Range selection is done by
means of the selector slider switch. Sensors can
be interchanged by means of the “sensor match-
ing” circuit in conjunction with the potentiometer
control in the sensor. This circuit also generates
the voltage level for the recorder output.
5 What is Luminance?
This is the amount of light as registered by the
eye. Luminance thus expresses the brightness of
a surface. The luminance in a certain direction is
the density of the illumination emitted from the
light-source surface, i.e. the quotient of the illumi-
nance J in the direction concerned and the illumi-
nating surface area A • cos
ε
.
The unit of measurement of luminance is the can-
dela per square centimeter = cd/cm²
or for very low luminance levels cd/m² (the former
unit was: “Apostilb” (1 asb = 0.31831 cd/m²)).
Also used:
1 fL (footlambert) = 3.426 cd/m²
1 cd/ft² (candela per square foot) = 10.76 cd/m²
A • cos
ε
A
ε
Probe
(7)
IC
cd/m² Segment test
Probe
Adaptor
Power Supply
Battery Monitoring
Segment test
Analogue
Digital
Converter
ON
Batt.
Recorder Output Store
D
I
S
P
L
A
Y