MODEL 1 5 3 MI CROVOLT- AMMETER
CALI B RAT l O: :
r a n g e s ,
th e
Mod e l
1 5 3
s h o u l d
r e a d
w i t h i n ±0 . 5%
o f fu l l
s c a l e . Ch e c k f o r
b o t h p o s i t i v e
a :-: d
n e g a t i v e
p o l a r i t y .
I f
n e c e s s a ry ,
a d j u s t t h e
ATTE�AT OR
A D ]
Po t e n t
i. o mL' t c r ,
R 1 3 7 ( F i.gu r e 20) ,
f o r
t h e p r o p e r rang e a c c u r a c y .
I f
p o t e n t i ome t e r
R1 3 7
i s
ad j u s t ed
f o r
a n y
r a n g e , r e p e a t
t h e c a l ib ra t i on f o r
e a c!l
ra n g e f r om
3
t o
1000 vo l t s
u n t i l a l l
r a n g e s
a r e
w i t h i n
t h e
req _ � r
e d
a c c u ra c y .
6- 7 . VERIF ICATION OF CURRENT
RANG E
CALIBRAT ION .
a .
Conn e c t
t h e Mod e l 2 6 1 P i c oamp e r e
S ou r c e
to
t h e
M
od
e
l
1 5 3 .
F o r e a c h
r a n g e ,
s e t
t h t:
Mod e l
2 6 1 f o r
a
f u l l - s c a l e i n p u t .
Th e Mod e l
1 5 3 s h ou ld
r e a d
\v i t h i n
: 1 . 5% f o r
t h e 3 n a n �
ampere t o
100 - m i l l i amp e r e
rang e s ;
: 2 . 5%
f or
t h e
l - n a n oamp e r e t o
10 0 - p i c o a mp e r c
r a ng c s ;
and
± 3 . 5 %
f or
the
30 and
10 - p i c oamp e r e
rang e s .
F o r
t h e r a n g e s
a b o v c
10 -4 , c on s t r uc t
a
c u r r e n t
s our ce ;
t h e Mod e l
2 6 1
ou t p u t
i s
n o t
s u f f i c i en t f or t he
h ig h e r rang e s .
b .
Th e
rang e r e s i s t o r
i n
t h e
3
t h r ough 10 0 - m i l l i amp e r e
p o s i t i on s ,
Rl44 ,
i s
s e l ect ed : )
a
+0 % , - 2%
t o l e ran c e
d u e
t o
a n
a p p r o x i ma t e 1 %
e f f ec t
i n
t h e l e a d r e s i s t a n c e
f r om
t h e
r �
s i s
t o r t o
c i r cu i t
l ow .
6- 8 .
RI S E
TIME
V ERIF I CAT I ON .
a .
Conn e c t
t h e
Os c i l l o s c o p e t o t h e Mod e l
1 5 3
OUTPUT .
Us e
a
s t e p
f un c t i o n
( t u r n
t h e
Mod e l
2 60 POLARITY
Swi t ch f r om
OFF
t o
+
o r
-
a s
r e q u i re d )
t o
t h e
Mo d e l
1 5 3
i n p u t
wh i c h
wi l l produce 100 ,
30
o r
10 -microvo l t fu l l - s ca l e r e a d ings .
Th e
r i s e t ime
(
1 0 %
t o
90 %
o f
fu l l
s c a l e
)
f or
a
fu l l - s c a l e
i
n
p
u
t
s igna l
s hou l d
b e
l e s s
than
1
s e c o nd
o n
t he
lOa - m i c r o
vo l t rang e ;
l e s s
than
5
s e cond s
o n
t h e
3 0 and
10 - m i c r ovo l t rang e s .
b .
Ap p ly
the
s t e p
func t i on f or t h e
I - mi l l ivo l t and
h
i
g
h
e
r rang e s .
No t e t h e mo t i o n o f
t h e
meter. I f
the
m
e
t
e r
shows
uneven trave l
t o
f u l l
s c a l e ,
i n c rea s e
t h e
va lu e
o f
r e s i s
tor
Rl27 (Figure 22)
t o
o
b
t
a
in
a
smoo th
mo t i on .
6 - 9 .
DRIFT
VERIFICATION.
Make
sure
the Mod e l 1 5 3
cover
is
on and
the
input
U
s h o r t e d
wi th
a
good
low
thermal short . Connect
t h e
Mode l
1 5 3
t o
the
M
od
e
l
3 70
Re c o r d e r .
Turn
t h e
METER
Swi tch to
+ .
Dur ing
t
h
e
f i r s t
two hou r s o f
warm-up ,
the
d r i f t
shou l d
b e
l e s s
than
8 microvol ts .
After
two
hour s ,
t
he
d r i f t
shou l d be
within
t2
m i c r ovo l t s
p e r 24
hours .
See
F igure
18
f o r
a typ ica l
d r i ft run for t he Mode l
1 5 3 .
6 � lO .
INPUT IMPEDANCE CHECK .
Put
a 200 -meg ohm
sh i e l d ed
re s i s t or
in s
e
r
i
e
s
wi th
t h e Mod e l
1 5 3
i
n
p
u
t
.
S e t
the
Mod e l
1 5 3 RANGE
S
w
i
tc
h
t o
1
VOLTS
and
t
he
FUNCTION
Swi t c h
t o
OPEN.
App l y
1
v o l t
to
the res i s tor with
the
Mod e l
241
V o l tage
Sup p l y .
The Mod e l
1 5 3
mu s t r e a d
a t
l e a s t 50% of
fu l l
s c a l e .
I f
it
does
no t , return
the
i n s t rument
t o
the
f a c t or�
,
.'
, I I ,
.. i :
'
'
I
22
,
i
,
'
!
!
t
__ . ,
.
\
. .
10 Ittc.c.tws
FIGURE 1 8 .
Ty p i c a l Mod e l
1 5 3
Dri f t Char t .
The in s t rument
i s s e t
on
the
10 - m 1 crovo l t
range
a t
var ious
inc r ea s ing
input shun t
r
e
s i
s
t
a
n
c
e
s
b e tween
s
h
o
r
t c i rc u i t and 20
megohms .
No i s e
incr e a s es
wi th increa s e
in shun t r e s i s tanc e
a s
John s on
no i s �
in
t h e
s hun t
a d d
i n
quadra ture
to
b a s i c
i
n
s
t
r
u
m
e
n
t
noi s e . Trans ien t s
o
c
c
u
r
i
n
g
a t
p o in t s
o f
s hun t
c hang e
a r e
d
u
e
t o
phys ica l changing
o f
t h e
shunts .
2 5
Summary of Contents for 153
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