MODEL
153
OP ERATING I N S TRU CT I O N S
1 .
M e t e r
j i t t e r
or
i n s t a b i l i t y ,
f r om
10%
to
20% of
f u l l
s c a l e .
2 .
High
o f f s e t
( d e
b i a s ) .
Rev e r s i ng t h e p owe r c o r d p o l a r i t y
o r r emov i ng
t h e
c o n n e c
t i o n
b e t \·}e e n
the
LO
a
n
d
GND
Po s t s
ma y
a f f e c t
t h e a
m
o
u
n t
o f
o f f s e t .
3 . 5 10\11
r e s p on s e
t i me . s l ugg i s h
a c t ion
a n d / o r i n c on s i s t en t
r ea d i ns b e t'''een
r a n g e s .
c .
To m i n imi z e
p i c ku p ,
k e e p
t h e c i rc ui t
awa y
f r om a c sourc e s .
Sh i e l d
a s c a r e f u l l y
as
p o s s i b l e .
Conne c t a l l
s h i e l d s t og e t her a t the
1 0\-1
s i d e
of
the
i npu t
o r
a t
t h e
LO
Po s t .
Th e
vo ltage
i n d u c e d
d u e
t o
a
ma g n e t i c
f lux
i s
p r o p o r t i ona l
t o
t h e
a r ea
o f
t h e
l o o p .
Th e r e
f ore ,
m
i
n
i m
i
z
e
l o op
a
r
e
a
s i n t h e s h i e ld
c onn e c t i o n s
a s
we l l
a s t h e
i npu t
c i r c u i t ry .
C o n
n e c t t he
s h i e l d a t
o n l y
o n e p o i n t .
Run
a l l wi r e s
i n
t h e c i r cui t a l o ng
t h e s ame
pa t h .
s o
t h e loop a rea
i s on l y
t h e sma l l d i f ference i n
pos i t i on
of
t t,'O
ad ja cent
td r e s .
d.
To
reduc e
t h e
e f f e c t
o f
ma gn e t i c
f i e l d s ,
u
s e
ma g ne t i c s h i e l d i n g .
"� e r e
h i gh
ac
ma g
n e t i c f i e l d s
a r e
p r e s e n t ,
i t
may
b e
n e c e s s a ry t o
mag n e t i c a l ly
s h i e l d t h e mea s u r i ng c i r
c u i t .
t he
unknown
emf
c i rcui t
o r a ux i l i a ry equ i pme n t i n
the
c i r c u i t .
Na g n e t i c
s h i e l d i n g
i s
a va i lab l e
f r om
s evera l
c
om
p
a
n
i
e
s
i n the
f rom
o f
p la t e s ,
f o i l
or
cab l e .
e .
Th e Mo d e l
1 5 3
l i ne
f r e q uency r e j e c t i on
r e f e r s
t o
t h e
t o t a l a c
v o l t a g e
a p p ea r i n g
a t
the
inpu t
t e rmina l s .
There fore ,
in
nu l l
d
e t
e
c
t
o
r
a pp l i c a t ions ,
i t
i s
a f f e c t ed
b y
t he
sum
of
the r i pp l e
i n
t h e
working
s t anda rd
and
the
unknown
s
o
u
rc
e
.
Because
o f
t h i s ,
work i ng
s t andard s
hav i ng
high
a c
r
i
p
p l
e
c omponents
wi l l
s i gnifican t ly
r
e
d
u
c
e t h e a moun t
o f
a c
vo ltage whi ch
ma y
b e
t o lerated
i n
the
unknown .
2- 1 2 . CIRCUIT CONNECTIONS .
a,
When mea suring
in
the
mi c rovo l t
reg i on ,
c
o
n
s
i
d e
r
the
e f f e c t
the ph
y
s
i
c
a
l c onnec t i o n s
wi l l
ha ve
o n
t h e pot en t ia l
b e i ng
mea s u r e d .
Vo l tage drops , whi ch
i n mos t c i rcui t s
a re i n
s i gni f icant ,
now
b
e
c o
m
e
impor tan t .
For
examp l e
No.
20 AWG
c o
p
p
e
r
wire
ha s
a r e s i s t a n c e
of approxima t e ly
1 0
mi l liohms
p e r
f o o t .
A
l-m1 1 liapere
c
u
r
re
n
t
t hrough a
6- inch
l eng t h
of
thi s
'Wi r e wi l l
c
a
u
s e
a
vo
l
t
a
g
e
d
r
op of
five microvolts .
To
reduce
this
d
r
o
p
b e l ow 1
microvo l t
wou ld mean us ing
a
wire
an
inch
long .
b ,
F our - terminal connections can o ften
be used to eliminate this error .
Re fer
to
F
i
g
u
r
e
5 .
c .
I f
a
sma l l
unwanted
vo l t age
d
r
o
p
1 s
cons tant ,
the
Z ERO
Co
n
t
r
o
l
may
b e
u s e d
t o
nu l l i fy
the vol tage.
d . I f
the
curren t s
or
r
e
s
i
s
t
a n
c
e
s i n
t
h
e
mea suring
sys t em f lu c t u a t e ,
t
he
y
wi l l
d eve lop
f luctua t i ng
vo l tag e s
w
h
i
c
h
wi l l
appear
a s
n
o
i
s e
o r d r i f t
i n
t he
sys t em .
Curre n t
Lead s
Mod e l 1 53
Lea d s
FIGURE 5 ,
Us i
n
g
Mod e l
1 5 3
wi t h
4- Termi na l
Connections .
2 - 1 3 .
OPERATING FROM SOURCE OTHER THAN 117
VOLT .
I f
the
a c
power
s
o
u
r
c
e
i s
234 vo l t s ,
u s e
a
s c rewdriver
to
change
the
1 1 7 - 2 34 Swi tch
on t
h
e
ba c k
pane l ( Fi gur e
3) .
Change
the fuse
from
0 . 5
amp e r e
t o
0 . 25
a
m
p
e
r
e
.
No o t her
a d j u s tment
is
nec es s a ry .
11
Содержание 153
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