-
17—10.
ELECTROMETER CONNECTIONS
397
17-9.
Description of the Instrument—The Dolezalek is the
most common of the many forms of electrometers (gure 17—10).
The needle is made of aluminum, at and gure—
eight—shaped, suspended by a gold,_ phosphor
'
bronze or platinized quartz ber between the
quadrants. The quadrants consist of a pill—box—
_
shaped brass chamber split into four parts.
-
Opposite quadrants are connected together With [
|
Wires, each pair serving as one xed conductor. ;;
.
_
:
The needle and quadrants are supported With Ïi
:
amber or quartz since great care must be taken
With extremely small currents to minimize
'
‘
any leak of the electricity. The apparatus is .+
surrounded by a grounded metal case, not shown
‘
in the gure, which cuts off air currents and
stray electro-static efïects or charges. The rota- Frs.
The
,
tion of the needle is observed with a scale and
Dolezalek electro'
a
telescope focused on a small mirror fastened
meter‘
to the suspension.
,
‘
17—10.
Electrometer Connections—Figure 17—11 shows the —
heterasz‘atz‘cconnectionforuse
’
'
in measuring the voltage v. -
_
P
’
The needlêN is kept at a high
___—__
potential(30
to l60 volts) by
_
_
’V ...:...
'
the battery [7
.
One pair of
—
:_
qu—adrants is groünclecl «and
_
Q
N
'
Q
the Other israised to the po_
f
_
“
;
is to be «
…
:
=
.
f
measured. AproteCt-iv'e re-_'
—
:È:G
.
. sistace
(&
_
,
.
1_“o4 tof10°
"
__…___|
i
batœfY
;
f
.
—
-
_
…
wandsuspenswn iñ' “case the “
,_
_
Fra. 17—11. “Hetèrostàtiéî’voltageconnçCüonneedleShOUÏd aç9ident3HY »