MODEL 1 53
MI CROVOLT - AMMETER
TAB LE 5 .
Tu h e
Go i n
V l O l A
10
V
1 0 1 B
1 0
V 1 0 2A
2 0 - 3 0
V
I
0
2
B
2 5 - 3 5
V I0 3A
3 0 - 3 5
App roxima t e
Amp l i f i e r
Ga i n s b y
S t ag e s .
5 - 7 .
INPUT
MODU LATOR
CHECK .
S ERVICING
FIGURE 1 7 .
D e mo d u l a t o r
Wa v e
Form
f o r
Fu l l
S c a l e I n p u t o n I - Vo l t
Ra
n
g
e
.
T h e
s ig n a l
i s
m
o
n
i
t
o
r
e
d
a t
t h e
j u n c ti ons
o f
c a pa c i t o r
C
l
l
a , r e s i s t o r R1 2 6
a n d
modu l a t o r
E I 0 3A ,
V e r t i c a l
s
e
t
t
i
n
g
i s
2
v
o
l
t
s
/
e m
;
h o r i z o n t a l ,
2
m i l l i s e c o nd s / em ,
a .
Remov e
t h e
d i v i d e r o f
F
i
g
u
r
e
1 3 ;
r emov e
t u b e V
l
O
I
( Figure 2 1 ) ,
S h o r t t h e
f e ed b a c k
n e two rk
to ground ;
s e e
p aragraph
5 - 8b .
S e t
t h e
RANGE
Sw i t c h t o
1
VOLT .
Us e
the
Mod e l 2 60
N
a
n
ov
o
l
t
S o urc e t o
a p p ly
a
+ 1 vo l t
i npu t s i gna l
t o
t he
Mod e l
1 5 3 .
Us e t h e Ty p e
P600 6 Prob e wi t h
t
h
e
Os c i l l o s c op e
t o
mo n i t o r
t he
s igna l
a t
p i n
2
o f
t u b e V IO L
( F i g u r e
2 1 ) .
A
typ i c a l wav e
f o rm
i s
s hown
i n
F i g u r e 1 6
f
o
r
a
p
r
o
p
e
r
l y
f u n c t i on i n g
m
o
d u
l
a
t
o
r
E IO I
( F i g
u r e 2 3 ) .
The
w
a
v
e
s h ou l d
b e
a
m
i n
i
m
u
m
o f
700
mi l l i vo l t s
p ea k - t o - p e a k
a v e ra g e
va l u e
( 70
mi l l ivo l t s
us ing
the
10 : 1
Prob e ) .
b .
Rep l a c e
a l l
t u b e s
and s h ie l d s ;
a l l ow
t h e
i n s t rume n t
t o s t ab i l i z e f o r
a f ew m i nu t e s .
5- 8 .
GA IN ADJUSTMENT .
a .
Th e Mod e l
1 5 3
ma i n t a i n s an
a pproxima t e ly
cons t a n t
f e e d b a c k f a c t o r b y c ha ng ing
the
amp l i f i er
ga in f o r each rang e .
I n
t
h
e
g a in
a d jus tmen t ,
t h e f e e d b a c k
n
e t
w
o
r
k
i s
sho r t e d
and t h e
cons tan t
eA i n f A r r n p �
A P P
r h pr k prl
b .
Short t h e
f e edb a c k n e twork
o n
t
h
e
Mod e l 1 5 3
b y
c o n n e c t i ng t h e
r e a r , d e c k
o f
t h e
RANGE Swi t ch ,
S l
(
F
i
g
u
r
e
1 9 ) , t o
t h e
c i r c ui t
l ow
t e rm i na l
o f
t h e
I N PUT
Re c e p t a c l e .
S e t
the
METER
S
w
i
t
c
h
t o
+ ,
the
FUNCTION
Swi t c h
t o
OPEN , a
n
d
t h e
RANG
E
Swi tch t o 30 MI LLIVOLT S .
App l y
a n inpu t s
i
g
na
l
t o
t h e
Mo d e l 1 5 3 , u s i n g t h e Mod e l
260 ,
s
u
f
f
i
c
i e
n
t t o
o b t a i n a f u l l
s c a l e me t e r r e a d i ng ;
n
o
r
m
a
l
l
y
thi s
w i l l
b e
b e t w e e n 300 a nd
40 0
m i c r o v o l t s .
S e t t h e
MET ER
Swit ch
t o
-
a n d r e p e a t
t h i s
p r o c e d u r e .
A
v
e
r
a
g
e
t h e
v a lue,
o f
t he two
i n p u t
v o l t a g e s n
e
c
e s s a ry t o d r iv e
the
me t e r
t o
ful l
s c a l e .
I f
t h e
a v e ra g e
i s b e tween 300
a n d
4 30
m i c ro vo l t s ,
t h e
l oo p
g a in
o f t he
Mo d e l
1 5 3
a mp l i f i er
i s
b e tw e e n
100
a n d
7 0 .
I f t h e
a v
e
r
a
g
e
i s
l e s s
t ha n
300
m i c r ovo l t s ,
a d d
r e s i s t o r ,
Rl lO
( F i g u r e 2 2 ) ,
t o
d e c r e a s e
t h e ga i n .
I f
t h e
a v e r a g e
i s
g r ea t e r than
4 30
m i c r ovo l t s ,
t h e
ga i n i s t o o
l ow .
c .
I f
t h e ga i n i s
t o o
l ow , e i t h e r
the
e f f i c i en c y
o f
m
o
d
u
l
a t
o
r
E 10 1
( F i gu r e 2 3 )
i s t
o
o
l ow
o r
the
ga i n
o f
a p
a
r
t
i
c
u l
a
r
a
mp l
i
f
i
e r
s ta g e
i s
t
o
o
l ow .
N o rma l l y ,
t h e
m o d u l a t o r
e f
f i e n c y s hou ld
b e
g r ea t e r t h a n
7 0 % .
Fo r
a
I - v o l t
i np u t
s igna l ,
t h e d emo d u l a t o r wa v e
f o rm
o n
t h e
I - v o l t
r a ng e
i s
s hown i n
F
i
g
u
r e
1 7 .
Ty p i c a l
s
ta
g
e
g a i n s
a r e
s hown
i n T a b l e 5 .
5 - 9 .
NOI SE .
S
e
t
t h e Mod e l
1 5 3
RANGE
Swi tch
t o
10
MI CROVOLTS
a n d s h o r t
i t s
i n pu t .
Me t e r
no i s e
mu s t b e
l e s s
than 3
m i n o r
d iv i s i ons ,
exc lus i v e
o f
a ny
t h e rma l
d r i f t .
S e t
t h e
FUNCTI Ot
Swi t c h
to
AMPS .
Shi e l d
the
i
n
p
u
t a nd c h e c k
me t e r
n
o
i
s
e
.
I t
s h ou l d
be l e s s
t
h
a
n
5
m i n o r
d iv i s ions ,
exc lus ive
o f
a n y
t
h
e
r
m
a
l d r i f t .
2 1
Содержание 153
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