
22-31Power Measurement
although characterized by a strong wavelength dependence, has a faster response and includes
ph
otoconductive
(s
pectral
ra
nge:
1–
12
μm) an
d
ph
otovoltaic
(0.5–
5
.5 μm) de
vices
.
e ma
in
po
wer
ra
diation
vi
sible and ultraviolet
se
nsors
ar
e
ph
otoconductive
ce
lls,
ph
otodiodes,
an
d
ph
ototransistors
. Ph
otodiodes
ar
e
wi
dely
us
ed
to de
tect
th
e
pr
esence,
th
e
in
tensity,
an
d
th
e
wa
velength
of li
ght
or ul
traviolet
ra
diations
. Co
mpared
to ph
otoconductive
ce
lls,
th
ey
ar
e
mo
re
se
nsitive,
sm
aller,
mo
re
st
able,
an
d
li
near
an
d
ha
ve
lo
wer
re
sponse
ti
mes
. On th
e
ot
her
ha
nd,
ph
ototransistors
ar
e
mo
re
se
nsitive
to l
ight
.
At ve
ry
lo
w
li
ght
le
vels