17—_10. ELECTROMETER CONNECTIONS
399
'
up on B and Q’, the needle is deected at a
on
the strengthof
the current from Æ to
K is a grounding key—
short c1rcu1t1ng the quadrants and is only opened at the time
readings are being taken. This
key should be closed when the Γ °"”“‘»'°“'"""'""""
battery 71 is rst connected, %
_
i
-
to
prevent the large induced }
__- _" —£
}
‘
:
charge on B from reaching the 5
;
-
-
l
,
quadrant. Itis important that :
_
:
the quadrant Q’, the key K 5
:
»
and the plate B be carefu/Zy }
'
l
'
rhie/ded at all times With a %
R
:
grounded metal case in order {
‘
Ï
:
_
to prevent the addition of in— l——-—
duced charges to those collect“
Ï
..
ed from be_…e_n çhe pla_æs
4
…
and B. Th13131nd1cated1ngconstant deection method,"
,
.
'
f
ure 17—13 by the dotted lines.
‘
-
”
.'
»
-
«
The constant deection met/zac! of measuring small currents is @;
more convenient than thépreceding method but'is not assensitive, Ë
l t is satisfactory down to approximately 10“13
‘
in gure 17—14,16 unknown
_
current
;
; high resistanceR
'
‘
i
i ohms) producing a
' _
{
drop (iR)which is
_
E K
,_
: terms
_
: …
{:_
small
.
_
_
:
+
_'
+
_
:
‘
must
btktïtth
.
: gddqdtdt
t___
_______,___
_…__--…J_
…:— "
.
'
Fog. 17—15. Balanced circuit
‘
lonsandelectr1Celds É
«gure 17—15, the unkn‘owpetnt1alœapphedwtheneedlean
Ï
One of the quadrantsmmsetoamdPœltlæpmn
[ “ground.
.
The gmund_ed pmnt°f°“°°f‘ïhebattenœlsvaned
399
'
up on B and Q’, the needle is deected at a
on
the strengthof
the current from Æ to
K is a grounding key—
short c1rcu1t1ng the quadrants and is only opened at the time
readings are being taken. This
key should be closed when the Γ °"”“‘»'°“'"""'""""
battery 71 is rst connected, %
_
i
-
to
prevent the large induced }
__- _" —£
}
‘
:
charge on B from reaching the 5
;
-
-
l
,
quadrant. Itis important that :
_
:
the quadrant Q’, the key K 5
:
»
and the plate B be carefu/Zy }
'
l
'
rhie/ded at all times With a %
R
:
grounded metal case in order {
‘
Ï
:
_
to prevent the addition of in— l——-—
duced charges to those collect“
Ï
..
ed from be_…e_n çhe pla_æs
4
…
and B. Th13131nd1cated1ngconstant deection method,"
,
.
'
f
ure 17—13 by the dotted lines.
‘
-
”
.'
»
-
«
The constant deection met/zac! of measuring small currents is @;
more convenient than thépreceding method but'is not assensitive, Ë
l t is satisfactory down to approximately 10“13
‘
in gure 17—14,16 unknown
_
current
;
; high resistanceR
'
‘
i
i ohms) producing a
' _
{
drop (iR)which is
_
E K
,_
: terms
_
: …
{:_
small
.
_
_
:
+
_'
+
_
:
‘
must
btktïtth
.
: gddqdtdt
t___
_______,___
_…__--…J_
…:— "
.
'
Fog. 17—15. Balanced circuit
‘
lonsandelectr1Celds É
«gure 17—15, the unkn‘owpetnt1alœapphedwtheneedlean
Ï
One of the quadrantsmmsetoamdPœltlæpmn
[ “ground.
.
The gmund_ed pmnt°f°“°°f‘ïhebattenœlsvaned