Philips pm2521 - Page 34

I
>1001
[
34
1.4. 2.2.
Alternating
voltage
measurements
(V^
)
a)
Input
a.
c.
attenuator
The
input circuit
for the
a.c. voltage
measurements
is shown
in Fig.
24.
The
table
indicates
the
attenuation factor
ADC sensitivity,
and range
relays
and
components.
The
basic
x 2 attenuation
is
given by the
voltage
division
of the
series
components
R101//C101,
Cl 02 and
the
shunt
components
R101,
R103,
R106//C103,
C104,
C105. Any
d.c.
component
at the input
is blocked
by
Cl 00.
-
x20 attenuation
is provided
by
R101//C106,
C107,
C108 switched
by
relay K101;
-
X 200 attenuation
by R
101 //Cl
09,
Cl
10,
Cl 1
1 ,
Cl
12,
Cl
13,
switched
by relay
K102;
-
X 2000
attenuation
by
R
101 //Cl
15,
Cl
16,
switched
by K103.
The
preset
capacity
trimmers
allow
calibration
of
the
different
ranges.
RANGE
ATTENUATION
AC INPUT
RANGE
RELAY
200mV
2
lOOmV
(RNGA)
2 V
2
1
V
20
V
20
1
V
K101
ReA
200
V
200
1 V
K102 ReB
2000
V*
2000
1
V
K103
ReC
*
max. input
=
600V
R.M.S.
C101
C102
Fig.
24. A.
C.
attenuator
detailed
ST 3376
811210