
16-6 Electrical Variables
In order to obtain the ac current waveform, a Rogowski coil is used together with an integra-
tor. Single-chip digital integrators have been developed to process the signal of Rogowski coils
(a
lso
kn
own
as dI/d
t
se
nsors)
fo
r
en
ergy
me
ters
. e us
e
of an AD 77
59
si
gnal
pr
ocessor
wi
th
bu
ilt-
in
si
gma–delta
A/
D
co
nverters
gi
ves
0.1% er
ror
fr
om
th
e
me
asured
va
lue
in th
e
10
00:1
dy
namic
ra
nge[15]
.
e Ro
gowski
co
il
co
ntains
no fe
rromagnetic
ma
terial,
an
d
th
us
it ha
s
ex
cellent
li
nearity
an
d
an
ex
tremely
la
rge
dy
namic
ra
nge
. Us
ers
o
en
re
ly
on th
eir
li
nearity
an
d
us
e
th
em
to me
asure
cu
rrents
th
at
are much higher than the ...